I'm using my salary to go to therapy, my mom is going crazy

I think you should keep going, because if therapy is making you feel relaxed, you must be heading in the right direction. I also went regularly for a year; my mom didn't understand at first, but when she saw the results, she quieted down. Maybe you can convince your mom a bit with the results.

I don’t think your mom is entirely unjustified, because therapy is an expensive thing and you need to be mindful of your budget. Just because you have an anxiety disorder doesn’t mean you have unlimited spending rights; that could be the point your mom is worried about.

Anxiety is already something that affects economic well-being too. If therapy seems expensive, consider a CBT (Cognitive Behavioral Therapy) approach. You can achieve quite effective results in just an average of 8-10 sessions. It can also ease financial worries.

Let me add this too, I'm actually not in debt but my mom reacts the same way no matter what I spend. There was the same stress before I started therapy, so it feels a bit like my mom's obsession.

What kind of logic is this? Is your mother opposing everything really the same thing as the current situation? You're talking about therapy, but you're not just throwing money at coffee. I can't say don't involve your mother, but I think there needs to be a little clarity in attitude.