How do you know if a person has a mental illness or is just mean and nasty?

[samilee39]

My adopted mother has always been cold hearted toward me.Now that she no longer needs my help taking care of my father and her mother(she was abusive to my dad and his mother when she lived withus)they both died 6 and 8 yrs ago.I don't know if she is mentally ill or just meaner now,especally after she recievced a great amount of money and took both of my inheratences and a 40k cd from me.she also has cut me from the will,i have done nothing to her to act this way. after my grandma died she got worst,I'm terminally ill and don't need this abuse all day all nite i have no where to go with my 14yr old son,i'm on ssi and unfortunately can no longer work.I also have depression due to my chronic pain and terminal illnesses, atleast that's what the docors say.She's making my health deteriate faster.My older son,brother and newfew don't say anything to her because she buys them homes, cars, ect..She tells me to die already, calls me nasty names,mistreats me and my younger son,verbally abusive and gossips and lies about me to friends and neighbors,church members and they believe her cuz of her age.I think her mind snapped after her mom died and she got a great fortune.she tells me she hates me everyday and just drives me crazy,i get out as much as i can,but don't forget i'm not well,on morphine and can't walk well.Do you think she was always mentally ill and got worst or just a mean nasty woman?