What should i do about this girl?

She was mean to me in school, snapping at me, treating me like dirt, criticizing my every movement, saying that she would slap me. Years later at uni I gave her a smirk when we bumped into her in the corridor. Then a few days ago when we bumped into each other in the corridor, she said hello casually. I pretended that I did not know her and she muttered something vile under her breath...when I changed my mind and said that I memba her she said loudly ‘NAH YOU DONT SAY..YOU BLANKED ME’....and then I said under my breath why would I memba you. Then when she was walking away I screamed at her what she had muttered under her breath and said you better watch your ****** mouth..