I recently told her that I would like to use them and they pronouns over her and she. I thought she would be okay with it as she has always been a supporter of the LGBT+ community. Heck, she loves going to pride parades! But she snapped at me and told me that she wouldn't use my pronouns. I don't know what to do...
Hello, Perhaps refuse to answer to her until she starts to use your pronouns. Once she starts to address you how she wants, she might slip-up a couple times as she's been calling you her/she for ages, but as long as she corrects herself afterwards then I'd still talk to her then. If she thinks of getting someone in for you ignoring her, then let her and you can just tell the person why.
Hi, Jo. I'm sorry to hear your mom didn't respect your wish. Secrets5's^ idea might work. Or you could try referring your mom with he/him pronouns to demonstrate the point of being denied being addressed with your preferred pronouns. Maybe if you take it easy for a while you'll feel up to talking to her again? Make it clear that this is important to you. And I mean, this is a question of simple respect, which is the bare minimum a parent should give their child. That said, it can take a while to adjust - but if she at least starts trying that will be an improvement.