Well, she's probably not allowed to own a gun anymore. At least one would hope, although the 2A in the absolute most unabridged sense says she probably can.
Anything can be misused as a weapon including a car, or a butter knife. A semi-automatic assault rifle is, actually, a weapon designed to murder. Let's not deflect to whataboutism or relativism. There are companies which sell weapons of war to ordinary citizens, sane or not, for profit. I'm not sure the authors of the Constitution envisioned this scenario. Nor did they envision "legal" ownership of guns by members of a militia for purposes of overthrowing democracy and the rule of law.