Or control/entitlement issues. First she brings up how honest she is and how she doesn't cheat. When that didn't work, she brings her daughter into it. When that fails, she goes for berating the chair ump, calling him a liar and a thief. Still not enough, failing to get her point back, now it's time to try sexism charges and waterworks for sympathy points.
Reminds me of a 4 year old brat pulling out all the stops to try and get what they want.
People keep focusing the words she said and compare them to worse words used by other players who didn't get penalized. But I think it had more to do with the fact that she, as Martina Navratilova mentioned, just wouldn't let it go. In what sport can a player just keep going at the umpire and NOT get penalized?