she is possessive, of you and your home, she thinks she owns the house, you are her servant and do ever thing at her bidding, she has trained you to pet her when she wants it, i would refuse to pet her if she is pestering.
a way to help solve this is get her off the couch/bed and get her one of her own. spend some time teaching her what it is ie get some treats that she likes and lure her onto the dog bed, she does not get the treat till her paw touches the bed, give her lost of praise, keep doing this till she learns to go on the bed with all 4 paws, then introduce the word bed(or what ever you want to use) this way you can get her to go to her bed and lie down.
i would put her on a lead in the house, even just a fine cat lead, and leave it on her, if your mums dog is going in keep a hold of it and give her a sharp correction if she makes any growl or bark or lunge at her(get someone to help you with this so your mujms dog can be on lead too)
do the same with your brother, she sees you as hers and he is trying to get near you so she is trying to challenge him. (you will need to watch her for this if your dating someone as she will not like to being intimate kissing/cuddling etc) so you need to nip this in the bud. praise her for any behavior that you like and ignore or correct her for any behavior that you don't like.
i would also control her meals make sure she has to sit a wait before she is allowed to dive into her bowl to eat.
teach her to give thing back to you so that if she gets something she isn't meant to she wont try to bite you to when you try to get it back. play trade with her teach her that if she lets go she will get something better, you can do this with 2 identical tenis balls no matter which one she has, the one you have must be the most interesting to bounce it and teas her with it and tell her "out/leave/drop/mine/thank you" etc just a word that means give it back to me.
hope some of that has lelped.