Friendship help

I started dating a friend within my friend group. Later on I found out she was lying to me about a guy, our group of friends never told me because they didn’t wanna betray her and spill her secrets.

I find out by going to one of our friends birthday dinner and the girl I was “dating” was there with the man she was lying to me about. Our friends knew, they argued with her that she shouldn’t bring him and. “Stood up” for me but they never told me and I was devastated when I walked in to the restaurant. I took some time off and didn’t hangout with them but sometimes I feel replaced by him. Should I just find new friends?