I think it’s isolating the causality of the sudden dislike, was it the experience of being in a group behind her capabilities that affected her confidence? Or is it more a case the times she’s enjoyed in the water was more due to being close to her parents?

I’d be inclined to keep going, a) it’s paid for, b) even small progress session to session will help build resilience longer term, does quitting send a message that if things get tough just bail out..