How do we keep my 90 year old mom from being evicted?

My 90 year old mother lives in a senior complex. My pot smoking nephew (also indulges in other substances) visits his grandmother quite frequently. Management accused my nephews friend of spray painting the garbage room, she also said that my nephew and his friend were hanging out in the laundry room and she also said that when on the elevator with my nephew he smelled of marijuana. Apparently the mgr. confronted my mother about these things (I'm told that she was very rude) the manager claims my mother threatened her, my mother says that she didn't. My mother has always been feisty, but I wasn't there, I don't know what words were exchanged. Anyway after 17 years of residency my mother has received an eviction notice from this fairly new manager. Can my mother file any kind of lawsuit to keep her apt? where would she go? what would her grounds be. I don't know if it counts for anything, but even if my mother told the mgr that she would kick her butt, there is no way that she could do it. Thank you in advance for your answers, your help is appreciated.