Maturity is in being able to take a step back and listen. Even if her assessment is fair. The guy is saying he was drugged, she believe he had mental breakdown, maybe the first thing is to see to it he gets help first and break up with him a little later. A “ruined party night” is peanuts next to the mental health of your partner. If it’s a new relationship, I get it. But if it’s been 6 months, she should start thinking about his health with more priority