Go yourself. in some states you only have to be 16 in order to get your own mental help. If she still wont and your underage that's neglect, go to a hospital if you have to, on your own. By law your mother HAS TO HELP.

if you are over 18 you will unfortunately have to do this on your own but the good thing is, your mother never has to know. Best to you, at the least call a suicide hotline. Please.