I've never given any gifts to any therapists I had, but it's also definitely not allowed here. I sometimes give a Christmas card though. I also never had a very good relationship with them, maybe a professional one but not like friends. I wouldn't feel comfortable with it, so that's the biggest reason for me. Because of money problems I also have to choose carefully, so if we aren't like friends I wouldn't do it. I already have to pay for the therapy and the therapists wouldn't buy me a gift or consider me a friend either. I may sound harsh now, but it just really isn't allowed and considered highly unprofessional here. I do give a gift sometimes to people who helped me out, but I don't have an official professional work relationship with. And I do a thank you care more often, also with people such as therapists, but only if they really helped me out or were nice. My parents also do it sometimes, but usually I can have a say in it too.
Apparently it's allowed at your place and you should do what you like. I do feel bad for you that your mom is pushing you like this though. And your therapist already knows she's going to get something, so I understand if you'd feel too uncomfortable to not give it now either. But maybe you can talk about it with your mom sometime?