I'd start looking for your own place and move out honestly. As long as you're paying their bills without consequence, they will continue to take from you. It's sad, but it's not uncommon for this to happen in a situation like you are in. I dont' think you should be paying her university bills in the first place. A parent, sure but not a sibling, that's just not your responsibility. if your mother cannot do so, then she needs to get a job and the only thing that will prompt her to do so is to just stop paying her bills.