what can I do to help?? she's his appointee but where. do I stand? NOT TTC BUT NEED ADVICE

So my boyfriend is classed as disabled and his mum is his apointee and always has been and apparently always will be, according to her he signed papers at 18 to say he wanted this but he has no recollection of this, now I'm 21 so is he and we're both in stable jobs and want to move out...but because she's his appointee apparently she's saying he has to have her say so and basically permission to do so..he's a mummy's boy and won't take her off as apointee...he's perfectly capable of handling finances and his life 
In my opinion she doesn't want him to go because he's her main source of transport due to the fact he has a car, we are wanting to move out but I don't see it happening with her involved as apointee, is it true what she's saying or???