(Changed my username)
My brother's in his late twenties and still lives at home. He's articulate, very able in certain areas, and does go out independently. He is also vulnerable. He's been taken advantage of and was nearly coerced into doing county lines. Luckily, it was dealt with by police and social workers and he didn't get into trouble. He regularly overshares on social media and became a laughing stock among my younger siblings' peers. He's been bullied and called vile names. I completely understand why my mum's overprotective of him (I also have an autistic son).
This being said, she totally infantalises him to the point where he's began to notice and wants to stop all his support and become independent. He now tells her not to plan her day around him -which is significant growth for him - and asks why she doesn't go out with friends, etc. On the other hand, he texts her from upstairs asking for a cup of tea and she'll bring it up for him. (He is totally capable of making a cup of tea, by the way).
She makes comments like, "Are you sure you want coffee at this time in the afternoon? The caffeine might stop you sleeping", at 4 pm.
We were having a nice day out the other day whilst he was out with support staff. Suddenly she rushed off home because he had a cold and she didn't want him to be on his own - although he'd have been more than fine with it. She cancelled her plans to go swimming the next day as well. It's a regular occurrence and part of the reason she barely sees friends anymore.
He has some neurotypical friends who my mum is distrustful of, not without reason but it's up to him who he hangs out with. He doesn't want professional support regardless of whether he needs it, and he doesn't want to make friends with other autistic adults (which his social worker suggested).
I've told my mum she needs to cut the apron strings and she thinks IABU.