I think you already figured it out; if the house does not belong to your mother, whether you stay or not is not up to her but up to your grandparents. You did not indicate how either of them feel about what your mother is telling you or whether they know what she is telling you. As you know, you are legally an adult now. Maybe she figured she no longer has a responsibility for you, even though you have a semester of high school remaining.
Check in with your grandparents, get them to agree you can stay and under what conditions (do they expect you to get a part-time job and pay towards your keep, for example?) and good luck!
Answered on Dec 30th, 2013 at 3:38 PM