<human>: Give me a shortened version of the text

I am friends with this girl.  She used to date one of my best friends.  They broke up, in quite possibly, the ugliest breakup I've ever seen about 2 months ago.  I took great care not to take sides and I still hang out with both regularly.  I was friends with the girl and her social group long before my friend dated or even knew she existed.

Anyway, I am throwing a rather major party. I am going to obviously invite my best friends, and since I still hang out with them, that girls social group.  Unfortunately, I can't invite her, because my friend and her can't play nice.  I feel bad because literally all her friends are going to be there, and I think she's going to find out even if I dont tell her about the party.  Is there a diplomatic way of telling her she can't come?  I dont want her to feel excluded or hurt her feelings, or make her think I'm taking sides.
<bot>: my friends can't play nice.  can't invite both to a party.  How do I tell the person not invited that she can't come without hurting her feelings.