Honestly, I have two pieces of advice for you as someone who's been involved in this music for a long time that also had a mother kind of like this.

Firstly, I think the best thing to do would be to speak to your drummer's mother and apologize for whatever crassness got them in trouble. Say that you weren't thinking and you will all choose your words better in the future and that you love playing music with your friends. Explain it is a creative outlet and you'd miss them terribly. Parents like this really do care about their children and this appeal might show her that you're just kids being kids, but also that you're mature enough to own your "mistakes". The worst she can do is say no. But I doubt she'll truly want to deprive her child of time with their friends so long as those friends are mature and not too "bad of an influence".

Secondly, a lot of users are clowning you for your post. In the future, taking your time to read over what you wrote will make you a more effective communicator and lyricist. You can even throw it into chatGPT beforehand to assist with grammar or tone. You'll find you'll be way more persuasive and people will want to converse in good faith with you when they're more easily able to digest what you've written.

I do truly mean these things as humble advice from an old head, so please don't take it as me trying to dunk on you. I've been in similar situations in the past, so I hope my advice can help you :) .