How do I do a friendship with a BPD Person?

[HiStrangers]

Hi everyone,

I dont know where to start. First, my english aint perfect 'cause it's not my native language. Second, I hope no one gets offended by what I am about to say and I hope you may understand me. To keep it private, I use they/them pronouns for the BPD Person.

The BPD Person ain't a family member, they is just a friend from college.

I'm currently in college and in febuary I met a person, later I discovered they had BPD.
I learn about mental health disorders in college so I didnt thought about it.
Well, my cousin has BPD too, and we have a great connection. So I thought I could handle her.
But in the last time I discovered that they tried to manipulate me. I dont know if they know about it but it messed with my mental health.
I cant just chat without thinking about manipulation, I cant even think about previous situation without thinking about manipulations, or ways they might have manipulated me. And I feel like I know that the whole friendship is build out of it. After our first chat (at day one) they told me "I am so happy, to have you in my life." A couple days later it changed to "I really needed (sounded more like need) you in my life!"
They always told me that "I am the only one who gets them" and that "I am very important to them". They kinda acts like they is my best friend, just because I listened and tried to help.
In the last few days, I was very busy with exams and stuff. I had no problem, I just didnt used my phone for a few hours to study.
I got 5 messages that were about "Are you mad?", "I am sorry, do you have problems, we can talk about it?".
I know that they tried to be nice and supportive but it really got on a nerve.
I always reply straight after I saw their messages.
They struggle with their self-esteem and self hate alot, and I always tried to convince them that they are good enough.

We hung out a few times but always for more than eight hours, also we saw each other in college daily. Due to Corona we couldnt see each other since april in college but we meet personally at our homes.

The last time was at a Shisha Bar, I dont know if you call it that way in other countries.
So we drank alcohol and smoked. Over the time they really got comfortable around me and talked about a lot of deep stuff. At one point they got triggered about talking about god and I did understand it and tried to change the subject. After that point they just said nice things to me like "you are such a good person" and "what would I do without you". And it wasnt just talking, it was like I could see it in their eyes that they meant it. Like really meant it.
After the bar closed, we waited for their Uber. They began to talk so bad about themself, that I just used every nice word I could find in my state of mind to comfort them. I was so worried, they might to something to themself.

They went silent and just stared at me, then they leaned forward and tried to kiss me.
I mean I would be flattered but they did know that I am in a happy health long relationship with someone, and about how much I appreciate and love this person.
It just felt like they didnt respected that. We never talked about it but since then I get daily panic attacks and anxiety when I talk about them, or with them. I feel like I need to be with them, cause they dont have anybody. I know that I was manipulated, many told me. But when I tell them how I feel, I am afraid that they might do something to themselves, it happened before after a friendship of them broke up. I dont want to be a reason for this behaviour and I really try not to become one. But while I try not to be manipulated the more I think they getting sad or mad at themself. They also manipulated me against a friend cause they said such cruel things and in the end it turned out nothing happened. The person with BPD admitted it, after I wanted to turn my back on them.
I want to get out of this manipulation circle but every time I try I get texts like "You dont care about me" or "no body likes me".
Is there an easy way, to get a break? Or just to show that I wont tolerate this behaviour.
Literally everytime I try to show them I wont tolerate it, it comes back even harder. Like threatening with taking their life or that they will do things so nobody will like me in the end.
I am so scared, that I wont even use correct pronouns here, so they might wont find this thread.
I just want to end this friendship, so I can find my own mental stability again.

Sorry for the long text, I dont know what to do.
I hope y'all have a great day and maybe some advice for me to improve my behaviour or how to deal with everything.

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[Football2000]

Even without the BPD I think there is another problem here, that you are hanging out with this girl who has feelings for you and you're in another relationship. So probably the correct thing to do here is keep some distance from this girl. Does your partner know about her? That could also cause problems.

[HiStrangers]

Thanks for your comment,
My partner just have seen them like two times so I wouldnt say they know each other.

I tried to keep distance but they asks me all day if  I am mad, or if I dont like them anymore!

I just shortly reply, so they wont get upset or stressed about the situation.
I get also get these messages if I am not online for like 5 hours, while they knows that I am busy.

I think, that if I tell them that I want some distance, that they might so something. Maybe in a bad way, but I am 70% sure they will be at my door shortly after.

I dont know if they has feelings for me, at this day a lot of alcohol was involved. We never spoke about the day, and I dont even know if they remember it.