1- She should go, but she should wear the full Hijab and not talk too much to her cousins. She can just say salam to them and that’s it. Not going to their house when they keep asking her to is a form of Qate’ Rahem.
2- She can talk to her cousins minimally by saying Salam and being very brief. Completely avoiding them and not talking to them when they want to say Salam to her is a form of Qate’ Rahem.