Thoughts?

My sister in law (let's call her Natalie) and I get on alright, we aren't close but we are friendly, anyway! Natalie has a friend (we will call her Sarah) and they are best friends but Sarah hates me (openly) because she thinks I made up I slept with her husband.. (I didn't, happily engaged) but it was just confusion by natalie because she knew I had been with a guy of the same name and assumed. Anyway that was over a year ago and I haven't seen Sarah at all in this time but now it's Natalie's child (my nephews) birthday party and she is guaranteed to be there and so will her husband (who thinks I told people i slept with him) 👎and Sarah's the type to try make me uncomfortable, she doesn't care... should I avoid the party or do i go and try my best to avoid her?