Before you do anything please verify how accurate her story is, whether she is intentionally skipping some details or just lying about something.
1. Hanging out with a new group of friends comes with a lack of trust where you must think about your wellbeing; in the first incident a guy tried to kiss her yet she didn’t think twice before hanging out with the same group where the same guy would be present.
2. Why was she all by herself? It implies that this guy might have planned it and asked everyone to leave him alone with her, if so then everyone who was present there is complicit.