Why do I feel bad after all she was the one that bullied me?

This is silly, I know. A woman in my neighbourhood I was friendly with turned up at a party of other neighbours. For the last couple of years she has been making snide, bitchy comments at me, but I have largely ignored her. Last week she went too far, and caused trouble between my fiance and myself - well I exploded! I called her every b***** and a******e under the sun in front of everyone - she was so shocked and stunned, she left the party in tears. Now I never want any dealing with her ever again, she�s a horrible jealous woman, but why do I feel so bad for standing up to this b***ch? She�s a real plastic 60 year old who pretends she�s 35, full of botox and sillicone, I�m just a natural 45, she turned to my fiance and told him to watch out for me, as I was only marrying him for his wealth - natural women are dangerous??? Oooh, I almost punched her! But I feel bad for losing my composure.