Is it normal that my mother prefers her step-daughter?

I am 57 years old and the older I get the more I hate my 77 year old mother. At 16 years old I was telling her something that happened during the day and she turned around & walked away as she did to me alot. I finally got mad and yelled "you never listen to me". Her reply back was Quote - "Everything that comes out of your mouth is boring. I don't have time to listen" Unquote. I was so taken aback/mad/hurt. I have lived with that quote since 16. Even now when she's done listening she interrupts me and starts talking about herself or other things. My sister just moved back into town living out of state for many years and now see's what I have been telling her. She does it to her now. She's rude to waitresses the way she responds to their introductions. She never asks about my children or grandchildren. And I don't tell her anything anymore. Remember "Boring". Everything is about her. She was a pretty woman when she was young and once told my sister & I - Quote - "I don't know what happened to you two" - Unquote. How nice is that? She didn't blink an eye. I did feel I got even when I was 34 & we went camping. Men TALKED and LOOKED at me. She was furious. 1 for me. I warned my almost new step-father not to marry her up to the day he married her. She has done nothing but belittle him, talk rude, wish he was dead, order him around, call him names in front of his friends, insult him. If you speak up to her she puts the blame back on you and says she's tired of everyone picking on her and she just tries to do her best and no one appreciates her and then sulks for days. It's not worth it to try to defend yourself. She's NEVER wrong. NEVER!! She can dish it out but she can't take any critism towards her. Nope! She has these new friends and she's always saying "They just love me 'cause I'm so funny". She's got a warpped sense of humor that is not funny to me. Never has been. Nor too my S-Dad. The other day we all got to together as a family along with her friends and she brought someone to the house to meet me. She went so overboard in trying to be funny about his being there. She and her friends were throwing a wedding garter at him to catch and making stupid comments and kept running into the other room where he was. My son was really getting P**'d and finally my son told her it wasn't funny. I told her the more she did it the more I would run the other direction and then she told me to "Lighten up, their only kidding" as she hissed at me. I wasn't laughing is what the problem was and neither was my son and daughter in law. They saw how rude she was being. The poor guy had to have been embarrassed. I did not talk with him at all. No chance to without being totally embarrassed. She told my sister & I on Mother's Day after she got her flowers and cards from us that her step-daughter sent her the most beautiful flower arrangement she has ever gotten and the card that came with them said everything so "perfect" that a card could say. Is this normal?