Sarah, there's no point battling with your aunt. She will NEVER HELP YOU.
You have to accept that. I know it's cruel, and harsh and horrible. It's horrible to think that your mum's own sister could be so horrible, but she is.
She doesn't think she is, of course not (nasty selfish people never think ill of themselves!), but of course she is. She's sacrificed YOU to make life easy for HER.
In your other thread you said your own mother would never want this miserable life for you, and you are RIGHT. No mother would (no good mother - sadly, not all mums are good - there's a post elsewhere about another member here who is my age - sixties - and who is being 'drained like a vampire' by a toxic mother who is leeching off her in her own home).
I know I've said this to you before, but NO ONE WILL RESCUE you - only yourself. Your father is a disgrace to my mind - he should have stormed in and physically carried you off, locked you in a room, then got social services to put your poor nan in a care home and THAT IS THAT.
As for your aunt, well, let us hope and pray, as BB says, that karma will come and bite her where it HURTS, so that she has as much misery in her life as you have had. She deserves it!
I do fear you know that you are locking yourself into some kind of 'fairy tale' where your ghastly aunt will 'see the light' and come 'rushing to the rescue' and make 'everything OK' for you.
But it won't happen. PLEASE give up on it.
Please, let your nan now be cared for by professionals, while you take up your long-deferred own life, and then spent 'lovely time' with your nan, visiting her and cosseting her and being the grand-daughter she has loved, but NOT keeping you from the life you SHOULD have. Please please accept that the way your nan SHOULD love you now is by SETTING YOU FREE.
I can't say different from that. Only you can do this, Sarah. Only you.
No amount of love for your nan, rage against your benighted aunt, disappointment in your father, can change that. Only YOU can save yourself now.
Please please just do so.
Kindest wishes, Jenny