I don't think that she was a mean person, I think, like everyone, that she had her flaws and these were a quick temper, speaking without thinking and lashing out at people when she was hurt or threatened.
If you mean her behaviour towards Mary, I don't believe that she ever tried to poison Mary but I do believe that she was mean to Mary at times and that she could have been more understanding of Mary's position and her feelings. I have copied the following from an article I wrote- Anne Boleyn and Bloody Mary (see http://www.theanneboleynfiles.com/anne-boleyn-and-bloody-mary/2670/):-
"We know from evidence that Anne often ranted about Mary and threatened to curb “her proud Spanish blood”, but Anne was a quick-tempered woman who felt backed into a corner and was just lashing out. Imagine Anne’s position: she is Queen of England but there is still a woman who declares herself to be the “true queen”, and who is still embroidering her servants’ liveries with “H&K”. This woman’s daughter is refusing to acknowledge Anne as the new queen, was once the legitimate heir to the throne, is a pretty and popular princess, and could be a real threat to Princess Elizabeth. Wouldn’t you be paranoid and defensive? I think Eric Ives is right when he says that any rantings and ravings from Anne were borne out of self-defence, rather than any malevolence.
There is evidence that Anne did try and forge a relationship with the defiant Mary. On one occasion in 1534, she visited Elizabeth’s household by herself and asked to see Mary. Anne offered to welcome Mary back at court and to help reconcile her with her father if Mary would accept her as queen. Mary’s impudent reply was that she knew of no queen apart from her mother but that she was pleased if the king’s mistress wanted to intercede on her behalf! How Anne must have wanted to slap her face! Anne did in fact try to reason with her, but to no avail."
I think that Mary did not help herself by antagonising her stepmother but Anne should've acted like an adult, risen above Mary's behaviour and kept trying to forge a relationship.
So, Anne was no angel but then she was also not the monster of "The Other Boleyn Girl" either.
What do others think?