u/Decent_Inevitable_31

So the situation is between me 28M and my ex 28F. On and off for a few years (5+ for various reasons), she had a boyfriend in between talking a couple of years ago. Recent months we talked January and start of February. She broke things off with me and we went no contact, previous to this I gave all the options for us to be together and she said she couldn’t do it. I accepted it and I ended up sleeping with a girl in my friendship circle towards the end of March. Fast forward to a couple of days ago she contacted me and wants to get back together. I have agreed to meet with her and talk through all the issues we had and see if we can get back together. Do I tell her about this? The girl is in my home friends friendship group and will be around time to time. It was purely causal, happened twice and won’t again. I am leaning towards telling her as if it does work I wouldn’t want everyone else knowing and she doesn’t. She is quite insecure sometimes so I don’t think she is going to take it too well. Any advice is appreciated.