Help how do communicate how her behaviour is hurting me

[Foolish man]

I am after advice please
As I have put in a recent post my ex girlfriend , has been on and off since November , came round to mine on Monday for dinner , she brought a friend and her behaviour was very erratic .
Playfighting a lot , long lingering stares etc then the pkayfighting got out of hand , and after she threw a cup of lemonade at me I threw a cup of water at her. This was followed by an hour of her being very nasty to me , her friend was emabarresed about some of the things she said .
The final thing that made me angry was she said to her friend get a fella for cooking , one for going out and one for sex .  I said that was cruel and a nasty thing to say and if she believed it she could leave . She calmed down and said you don’t really think I do that do you .
Her friend then left the room so we could talk. We were very close together talking and I was saying how I felt about her and she was taking normally . Then suddenly she told me she had had sex last week, whilst we were in a no contact period indicated by her. I asked how it happened and she said things just got out of hand and also said just like when we got together . She also said that she was having dinner ( tonight ) with someone but don’t worry it’s not the one from last week .
I didn’t know how to handle that and just went for the I love you I don’t like hearing this stuff and tried to kiss her ( our faces were very close together ) and she pulled away and said. No .
After that long explanation my question is how do I get her to understand that hearing these things really upsets me and that it is cruel . She knows how I feel about her .
I am really struggling to set boundaries and think that this could help us .
By the way she was the one who broke the no contact

[PLEASE - NO RUN MESSAGES]

PLEASE - NO RUN MESSAGES This is a high level discussion board for solving ongoing, day-to-day relationship conflicts. Members may appear frustrated but they are here for constructive solutions to problems. This is not a place for relationship "stay" or "leave" discussions. Please read the specific guidelines for this group.

[itsmeSnap]

Hey man

My reply is a bit long but I'm thorough like that

Playfighting a lot , long lingering stares

You mention she was erratic. Was this out of character for her? Who was playfighting, you and her or her friend?

she threw a cup of lemonade at me I threw a cup of water at her.

I know its a thing of the moment, but don't throw things at people 

Ok so I'm trying to be a little light here but its serious stuff, matching aggression will most likely lead to escalation and more serious fights.

Remove yourself when that happens, give everyone room to cool down.

she told me she had had sex last week, whilst we were in a no contact period indicated by her

You are not exclusive, she's seeing other people. This hurts you, it seems like the relationship is not on terms you like correct?

I asked how it happened and she said things just got out of hand and also said just like when we got together

People with BPD tend to be impulsive, she mentioned it happened before, and it happened with you, it will probably happen again. Are you ok with that?

I didn’t know how to handle that and just went for the I love you I don’t like hearing this stuff and tried to kiss her ( our faces were very close together ) and she pulled away and said. No

It sounds like you love her very much, she sounds like she's not so sure, and this is hurting you.

You said you've known her on and off since november is that correct? How much of that time has been "on"?

how do I get her to understand that hearing these things really upsets me and that it is cruel . She knows how I feel about her .
I am really struggling to set boundaries and think that this could help us .

The goal is not to ask for guilt admission, but to end the conflict entirely, subtle difference. There's an article and video here about ending conflict here [https://bpdfamily.com/content/ending-conflict]

From the post I gather you feel you are not being considered as part of a relationship. She rejected your advance, she said no. Give her space, give yourself time to truly consider the relationship you have and want to have with her.

Before you can set boundaries you need to think hard and honestly about where you draw the line, she will likely test it and try to trample the boundary, she might split you again, perceiving it as you doing her wrong. This takes strength, if you give an inch they know to take a mile, if you pursue when you shouldn't they know they get their way anyway.

Think hard: what specific issues would you like addressed as a boundary?

[Foolish man]

thanks for your reply
An highly edited background is .
We met in August, first started talking on line when she was with someone else, not flirting but helped her with some problems. She finished with her boyfriend, and we spent some time together , she moved n within a month and she  finished it by early november. Moving out took a while but we remained in constant contact. spent a lot of time together over christmas , got bakc together new years day and then it she finished it again a couple of days later. here is a big age difference between us more than 20 years, but all of her boyrfiends have been a lot older. She broke it off beacuse she said she wasnt happy and i was gutted but understanding.
so much more has happened but that really is the edited highights.
to answer your questions
she was sometimes like this but not so animated and not for so long, her and i were playfighting.
the water was a playfull thing, but i was a little annoyed she threw lemonade over me, and i could have responded better.
we are not a couple as she had broken t off with me, but she knows how i feel about her so she knows what she said would have hurt me.
It didnt reaslly happen like that for us , we had a couple of netflix dates first as i was a little concerned about the age dffference, and no i definitely wouldnt be happy if it happened again, i really cant stand cheating and it is something i have talked to her about in depth, due to previous relationships.
I understand she may not be sure about us, but she keeps coming back so i assumed that there are still feelings there.  I understand about BPD behaviours but most of her ex she cut out immediately although then still messaged them. She is always on her phone messaging , mostly male admirers who she says she only gets on well with men and doesnt have female friends. ( she later admitted she knew these men were trying to get with her but it shouldnt matter as if i trusted her then there wasnt a problem)
As i am typing this i understand it sounds crazy why i would want us to be together but i have such deep feelings for i cant seem to let go ( counselling is already booked in for me)

[Foolish man]

The boundaries I would like are when she says these hurtful things and my reaction to them. Although I was calm I still didn’t react the right was as telling someone who is unsure and possibly splitting me that I love them will only drive them further away as it sounds ... well just desperate ,but that is how I am feeling
Kinda obsessive as well
Maybe I should just stop ,but I think that would be even harder than this pain

[itsmeSnap]

As i am typing this i understand it sounds crazy why i would want us to be together but i have such deep feelings for i cant seem to let go

Does it sound crazy to you or because of how others might react?

Don't worry man, we have a big "please NO RUN MESSAGES" box below the threads, we understand its about making things better.

Also, this is about you and your reactions, just know there's not much to do about her shenanigans other than how you react and frame your interactions, she also gets to decide how she handles her life whether you agree with it or not.

Lets get right to it 

It didnt reaslly happen like that for us , we had a couple of netflix dates first as i was a little concerned about the age dffference, and no i definitely wouldnt be happy if it happened again

Ok so you know cheating and seeing other men is not ok. From your story I gather she's mentioned she is in fact seeing other men (dinner, impulsive sex) and talking to them on the phone.

The boundaries I would like are when she says these hurtful things and my reaction to them

I guess first is for you to know and define at what point has she "crossed the line"; giving up on your values for the sake of a relationship can end up in a difficult place.

telling someone who is unsure and possibly splitting me that I love them will only drive them further away as it sounds

It might, might not. Its ok to tell someone you love them.  it hurts when they don't reciprocate, don't be too hard on yourself.

Maybe I should just stop ,but I think that would be even harder than this pain

You're in good company man, people here understand. some are in similar situations, other went through that and stuck around to share their experience. You're not alone in this.

Stick around