I have a friend who I was very close to, and whom I shared a lot of personal information, thoughts and feelings with, as a best friend. She shared things with me too, but she lives at home with her Mum and isn't in a relationship so we would often discuss my side of things more.
She has made a few mistakes during our friendship which have caused us to fall out but she always apologises, sending flowers and leaving notes, sending messages etc. I have been told by family and friends that I'm too nice for my own good and tend to forgive when I shouldn't but we've been friends a long time (since school).
Anyway recently had some serious issues in my personal life (cheating stbxh, divorce, money problems, elderly relatives becoming more dependant) and I found out that my friend had been discussing everything I had confided in her with someone else who is going through a similar situation.
My friend did not admit this until I confronted her with proof, then began apologising, begging forgiveness etc. Her excuse was that she thought I could make a new friend with our shared experiences. 
I felt very hurt and told her I needed space for a couple of weeks to get over it.
This 'friend' is now telling mutual friends (some of whom are my dp's work colleagues as they work in the same office one day a month) that I've fallen out with her and that I'm lying about why, implying it's something I have done. She keeps posting pointed quotes etc on Facebook, I have now blocked her as it's making me upset.
My dp is at a team building dinner tonight and she will be there, (not sure why, as she has recently resigned from the company) I have asked him to not mention me or answer any questions about me.
WIBU to send her a message telling her to basically shut up about me and my personal business, and that our friendship is over? Not sure how to word it but I can't help but feel I need to address it instead of letting it slide again.