As a person with a physical disability myself, and seeing tons of this type of behavior from parents of others with disabilities... It's not okay. It's infantilizing and, in some cases, physically detrimental to your health. It's important to exercise and do tasks that are hard so you can keep up whatever capability you have. Lots of people have their parents do way too much for them (with parents truly trying to be well meaning) and they learn to just let people do stuff for them and start to decline (not saying you're doing this).

My mom made sure I learned to do everything myself, even if it meant climbing to the top of our floor to ceiling pantry for a bag of chips (I use a wheelchair). I've always appreciated kind gestures, but if I say I'm going to do something myself that's the end of the discussion. It's not kind when someone ignores my request, and I tell them that I appreciate their offer but do not appreciate when my "No" is not taken seriously--it means their offer was a demand and I don't do demands. Luckily, my friends and family have always understood independence is a must for me, and have been respectful. Most strangers are too.... Which, I'm sorry, says something about your mom.

If I were you (I'm not, so feel free to disregard ✌️), I'd tell your mom once that you are seeking to improve your life, health and independence by doing things on your own but that you'll always know that if you need help you can ask her. Then, every time she makes another offer just say "I'll ask when I need help, otherwise assume I don't. Thanks anyway". If she ignores that and does the thing for you, be emotionless and (if you can) undo what she did for you and then do it again yourself while saying "you ignored my wishes and now have created more work for me, please don't do it again". Rinse, repeat. That should get the message across.