I can relate to you because my mom talked to me about similar things from the time I was 14.
I must ask, how long has this been going on? Even if you are over 18, the dynamic of the mother-child relationship will be the same in many ways.
-Shelle

Hi Shelle,
Well, it's been going on since I was a child really as I remember a conversation I had with another 6 year old, telling her not to have kids and to never trust men. Anyway, it took me a really long time to get a boyfriend (I was under the impression she wouldn't love me as her little girl if I did that and also, because I was sexist towards men for a long time). When I finally did get a boyfriend, that is when she figured she could talk to me about sex. I am 26 now, so this has been going on for a few years.
She also "matched" my best-friend who is 8 years older than me with one of her work colleagues with whom she is friends. Now, I know my friend chose to be in a relationship with this guy after all, but I felt like I had lost my best friend in a way because sometimes my mum would say things like ":)id you know that your friend is doing this... .haha, I knew even before you!" Because obviously, she had been talking to my friend's boyfriend (now husband). This also damaged my friendship, but we are still friends, and yes, she talks about her sexuality to my friend as well. My mum also wants to go on vacations with the two of us. Ugh.
Anyway, I told my friend (who also has a BPD parent, so I think that's why she kind of fell under my mother's spell) that my she should avoid sharing so much with my mother, as now my mother feels like she has jurisdiction over her.
I suggested she see a therapist in the past, and she agreed, but never followed through. She wrote to me again about another crisis and I mentioned the same thing, so we'll see. I helps that I have recently moved abroad for my studies though, so I can wait a bit before responding to her cries for help and can be a bit vaguer in my responses so as to not get too involved.
Another thing that bothers me is that, I feel like she can suck information out of me that I wouldn't normally give to her, but feel compelled to in some way and then regretted it.
There are times when I feel like our relationship is fine and I am in control and then obviously, there are times where I am totally overwhelmed.