boyfriend going to a party with an ex

So my boyfriend is going to a party tomorrow which he invited me to but I'm going away so I can't make it☹️️ but basically a girl he used to fuck(it was always non emotional for them both) is going (he also got her pregnant a couple years back) and I really don't feel comfortable with them talking and being with eachother he said he's going to ignore her but I'm having such anxiety. She said to me at another party she'd never go back there and wouldn't do that to me but she has a bit of a reputation so I don't trust her. I trust my boyfriend enough and I know he would never go back there or do anything to hurt me I'm just so worried and don't like the thought of them being with eachother. Am I overreacting?