I cannot leave the group I am in. I am one of the two co-founders and I am in charge of the BIG project we are currently doing. Plus, I am incredibly passionate about the group. I've probably put in 100 hours to get this group off the ground. It's related to my career and it would damage my career significantly if I just dropped it, given that I started it, publicized it, and convinced several colleagues to join (NOT her!) She found out about it because of all the publicity I did, and joined without my knowledge.

I also probably should have mentioned that she is "above" me at work. It is very difficult for a junior faculty member to complain about a more senior faculty member. I am in an even worse position because, last year, I was being SEVERELY sexually harassed by a male colleague who harassed 4 other women before me. When I found out I was not the only one, I went (with the others) to the chair and I complained. He was ultimately fired. However, it would look like I was the problem if I suddenly complain about being harassed a second time-- even though it is clearly happening. As the most junior faculty member in the department, I just don't have the clout to file a second complaint without it likely damaging my career.