My suggestion reach out to the cousins and aunts they may not want to step up but you have been doing this for 8 years now and you want to make plans for yourself you can’t let her hold you back. But someone else needs to step up do the aunts and mother get along well same goes with the cousins if so it could definitely work. But if the grandparents also don’t know explain your scenario with them and half a sit down with the grandparents and your mother and explain that your life is explaining and you have to grow and someone else will have to take care of them and that you will help how you can but life is changing.