She, or anyone else with knowledge of the situation, is allowed to contact child protective services and report neglect or abuse. If she's got a roof over her head, reasonably sanitary living conditions, food on the table, and several changes of weather-appropriate clothing, CPS isn't likely to support a claim of neglect and remove her from the home (and if they DO remove her, THEY get to say where she'll go; likely to foster care).
Emancipation would require her to go before a judge and show that she has an excellent scholastic record, no behavioral problems, and has an established track record of earning enough to completely support herself, including rent, utilities, health insurance, transportation, food, clothes, and all the other necessities of life without assistance from anyone else (including having "roommates" or living with anyone unless SHE can cover ALL of the bills by herself). Less than 1% of minors applying actually GET emancipation, especially if the parents aren't 100% willing to sign off on it. It's not meant to be a way out from under parents, it's meant to be a way for children already forced to care for themselves to have a little easier time of it.
If there is another stable and responsible adult willing to become her legal guardian, they can file a guardianship case in the local county probate court and argue that it's in the child's best interest to become the legal guardian instead of the mother. If mom fights it, the odds aren't good unless there's some drastic and DOCUMENTED history or neglect, abuse, or other egregious conditions or behaviors going on. Parents are ALLOWED to yell, allowed to treat their children differently, and are allowed to be "bad" parents. None of those things are a ticket to getting out.

