Literally asking for a friend🤦🏻‍♀️

So my friend and i were talking. Her current boyfriend, she loves him with everything in her. Like the thought of losing him makes her heartache and go into a depressed state, however the first couple years of their relationship he cheated on her up until about now. The last incident with him, he was talking to his ex and they rekindled and he broke up with her. The same weekend he broke up with her he spent a weekend with his ex and did god knows what. So when that happened, I convinced her to go out with me and all night she was avoiding guys all because she felt like he was and still is the one. Well fast forward to today, her boyfriend came back from his trip to see his ex and basically decided she was the one he wanted to be with. And besides a few “get rid of your tinder” talks, he has been pretty loyal to her. However, she is now in a weird place. She and I went out and she ran into one of her old flames, and say flame because, because of her current boyfriend she never actually dated this guy. So they talked and caught up, well they started messaging and she’s done caught a crush for this guy, and she is not physically cheating but has been flirting. She doesn’t want to take it any further because she doesn’t wanna hurt anyone. She doesn’t want to loose her current boyfriend, but catches herself flirting with this old flame, and now a guy she works with...but again just flirting. I told her I didn’t know what to tell her, so I’m asking for advice for her and to give to her. What should she do?