Bringing another girl around ex-girlfriend, what could be the consequences?

So I dated this girl for about 2 months, and we broke up because we moved too fast and she still had feelings for her ex-boyfriend of two years. I didn't want to end things but I guess it had to happen. We have been broken up for about a month now. Since then we have hung out as friends a few times and still get along really well. I have been talking to a new girl for a few weeks now, its nothing serious but we have a lot of fun together as well. This saturday night, my roommate is having a birthday party and ex-girlfriend will be there. And I was thinking about bringing the new girl. I think the ex knows I have been talking to someone else but it hasn't been brought up in conversation, but I'm pretty sure she's heard about it from our mutual friends. I am pretty sure she still has feelings for me she just hadn't got over her old feelings for her ex yet. Part of the reason I haven't told her is because I don't want to screw things up in case there was a chance we would get back together. Should I bring the new girl?
Bringing another girl around ex-girlfriend, what could be the consequences?
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