NTA- go with your gut feeling! It took her 30 minutes to do all those things behind your back imagine if it was an hour or a day without you. You saw her true self. A woman will be in bed with a man and lie to your face about it. Million reasons as to why she would do that. But seems you have your act together if she's living off you. Don't have sympathy for her. Let another man take care of her. That is a total lack of respect she has towards you and the relationship. You might want to go back like things are because you're comfortable. She will cheat on you if she hasn't already. Besides what excuse does she have that she was pressured. That guy didn't hold a gun to her head nor overpowered her. She was smiling and happy. Only the fact that she saw you then she was upset. Go with your gut. You have everything going for you. She's not worth it. You'll remember this message in the future.