I lied to one of my friends, and I feel bad about it. I just  dont know how to tell her the truth. 
Just tell her? She will be grateful for the honesty.
Ugh... shes literally about to get married and her boyfriend has been cheating on her. I am scared to even bring it up. 
Dang, that's rough. I wouldn't know what to do either. It's like you choose to be a good friend and destroy their marriage or let her get married so she's happy. Goodl uck