<human>: Provide a brief overview of the text.

GF and I have been dating for 18 months. Her ex, Bianca (not real name), who used to hang around with a separate group of people, recently got "kicked out" of that group for causing so much drama and tension (I this all through a 3rd party). Bianca started hanging out with me and my girlfriend's group of mutual friends, and has been brown-nosing like crazy and inviting herself to a lot of events. Nobody in the group knows about her past drama, and they all think she's perfectly nice. 

The issue is that it makes me just plain uncomfortable being there when Bianca is around. I had never met her before, but she had still managed to spin up a lot of drama with my GF, especially when they broke up (GF dumped Bianca for me). I don't want to start trouble, so I haven't told any of my friends anything about how I feel--in fact, they don't seem to even know that Bianca and my GF were ever together. It's causing tension in our relationship, because I don't like going to events if Bianca is going to be there since it makes me feel so shitty, and GF doesn't want to tell any of our friends that Bianca and her used to bang and now it's awkward. I feel resentful of my GF for not doing something about it, but at the same time am not sure what I even want from the situation. How can I deal with this maturely? Do I have much of a choice other than to just start hanging out with other people?
<bot>: My gf's ex is hanging around our friend group and it's driving me insane and causing tension in our relationship. How can I be an adult about it?