I’ve been playing drums professionally, probably as long as you’ve been a bassist. RECORD the songs you are talking about. Record the songs and discuss everyone in the band’s performances. Don’t just single her out. But, show her how she is screwing up. If she doesn’t immediately start working on improving her playing, you’ll realize she isn’t serious.
This is great advice, often repeated. It only works on self-reflective proactive people though, which are few and who are seldom an issue in a team environment.
It's the equivalent of saying "Hey Fatty, there's a gym over there!". Won't change a thing.
Same as working with someone, effectively giving them free lessons ... will they practice with focus at home? No. They'll value your time and experience for what it's worth - nothing - because you gave it for free.
OP said it's all for "fun". Well, fun is doing things right to get things right. If someone's not doing that, it's no fun for those who do.
Ideally everyone in any band is pursuing development on their instrument and growth as a musician. This is done through focused practice preferably with the input of an experienced teacher or mentor.
If not, recordings won't matter. They either won't / can't hear it, or if they cared they'd have already worked on it.
Same thing in relationships, in the workplace, etc.
It comes down to values, and it's rare you can change the values of others. Only consequences *might* do that, so ...
Fire the drummer!
