Boyfriend's ex appears to not be over him?

I met my current boyfriend in August of last year and everything is going really well, however we have ended up at the same event as his ex-girlfriend a couple of times during that time whom he broke up with three years ago. Her being at the same event as us is in itself absolutely fine, however both times she has decided to stand very close to us, ended up going to the bathroom at the same time as me, and came and stood next to me at the bar the one time I went up. The first time this happened it could be passed off as a coincidence but as it has now happened twice I strongly believe it's intentional. This has made me feel very uncomfortable and I don't know how to navigate this as I assume that she is not over him yet. My boyfriend has given me no reason to doubt anything in our relationship at all, however it appears that this will probably keep happening and my empathy for someone who purposefully is making me uncomfortable can only go so far. Does anyone have any advice or thoughts?

Boyfriend's ex appears to not be over him?
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