Background: I am a guy who has traveled quite a bit across the U.S. and made a lot of friends due to an organization that I am a part of (not work related). Last year I went to visit some of these friends in another state and they brought along a few people I had not met yet, and we got to know each other over the course of a weekend. We exchanged contact info and parted ways.
One of the people that I had met needed some help with navigating a few things in our organization that she was learning how to do, and I had previous experience doing them so I offered to help. We began to communicate frequently and I gave her the advice she needed. She is an interesting person and we chatted about a lot of other things via texting/email as well. Note: We do not see each other regularly due to the distance that is separating us
Pretty quickly though, she started to message me a ton and some of the conversations got way too personal for my liking. I asked her to back off, but she would only leave it for a week or two before trying to get too personal again. She also started to tell me a lot of very personal things about her life that I was not interested to learn because we were just casual friends.
Recently I felt very bombarded with how much communication that we were having because it was pretty much nonstop and she wanted me to provide her a lot of emotional support, other advice, and for me to tell her all about my life and past etc... I felt smothered and bombarded and also I just wanted to be casual friends. I had learned from some others that she has some issues with respecting people's personal boundaries, and I had begun to feel that in my own life when she started asking me very personal questions (past relationships, my battle with depression, about when I would next start a relationship, and questioning a lot of my personal choices).
I wanted to create some distance in the friendship so I started to drop hints that progressively became more and more blunt but she still didn't get it. Unfortunately, they didn't translate very well to her, and she continued to bombard me further. Eventually I just straight up told her to please stop bombarding me with messages etc... Even after telling her that, she continues to message me, and is quite upset with me.
Naturally she is very upset by this and doesn't understand why I am telling her to back off. Originally I tried to ask her nicely, but she just didn't get what I was telling her so I had to be pretty harsh.
She also recently told a close friend of mine (a girl) who I was considering asking out on a date (she liked me and I liked her etc...) that she could never date somebody like me blah blah blah. Basically it ruined that friendship beyond repair, and I do not want it to happen again with my other friends. I have since ceased communication with her and no longer respond to any of her messages.
We have a large mutual friend pool due to both being in this organization, and I am concerned that this may happen again.
Question: My biggest concern through this is that I will lose the mutual friends that we share, since she is close to them and spends a lot of time with them and I rarely see them. I am very close to these mutual friends and have known many of them for 10+ years. I do not want to lose those friends because of this situation, but I feel like it could be a big possibility.
How can I preserve those friendships while still ending this one? Is there a way to avoid the collateral that is inevitable in the near future?
Also, how can I explain this situation to these friends without it sounding like I am bashing this girl?
EDIT:
I also just thought of this as well, since I likely will have to interact with her in the future due to our organization, What is the most professional way to interact in the future? (This may be a topic for another post)