When DF and I had been dating for about 4 months, we went to a fairly nice new restaurant to celebrate him getting a new job. Our waitress was a girl he'd gone to high school with but hadn't seen in the few years since high school, and he didn't really seem to remember her. She had to introduce herself and remind him of the classes they'd had together. When he finally did remember her (which he later told me he really didn't but it was so awkward he just wanted the moment to end), she giggled like crazy and said he was always such a silly guy and grabbed his shoulder and started to sort of massage it. She took his drink order and started to walk away, so I said really quick "And I'll have a coke as well" and she turned around and looked surprised and said "Oh! Ok." She brought back a coke for DF and a diet coke for me. I told her right away that it was diet and she argued that I had ordered that. I said I hadn't, I can't drink the artificial sweetener, so there is no way I would ever order a diet drink. She finally took my drink and then turned her back to me and leaned her butt on our table towards me and started talking to DF and asking what he'd been up to since high school. He said he just got a new job and so we were out to celebrate and he called me his girlfriend and gestured to me. She looked at me with surprise again and said "Oh! Ok." again and walked off. She brought back a regular coke and took our orders. DF's plate was almost overflowing with food and he somehow ended up with an extra side of lobster bisque and when he pointed it out, she said to just keep it because the kitchen couldn't take it back. My food however, was slightly overcooked (medium-well instead of medium-rare) and my sides were very tiny. I chose not to say anything as it was still just within the bounds of reasonable portions and I didn't want to have to wait for a new steak. DF noticed and gave the extra soup to me since he doesn't eat seafood anyway. When the waitress saw me eating the soup, she laughed and said to DF "Those darn girlfriends, always stealing your food!" and offered to bring him a new one, which he declined and he also said he gave it to me because my food didn't look as appetizing as his. Every time she came to our table, her back was to me and she found some excuse to reach out and touch DF. At one point, she even sat down in the booth and tried to say they should get together for coffee and catch up, while leaning up against him! Poor DF looked so embarrassed, and he apologized so much in the car on the way home, but it wasn't his fault, of course. He was convinced I was going to break up with him after that though, he was so furious with her for what he thought would end his relationship for sure. When she brought the check out, I made a point of saying "Oh no, let me get this, Sweetie" and the look on her face was just priceless. That is one of the only times I've not tipped someone.
I just can't understand why you would ever ignore or be pointedly rude to any member of a party. When I waited tables in college, everyone I worked with was very aware of being nice to everyone and most people made a point NOT to flirt with anyone at a table, specifically because it would lower your tips. I don't know if we just had really good people working there or what, but that just wasn't considered acceptable. The couple of new people who would try it out would quickly learn why no one else did it and get teased in the kitchen if another waiter saw them do it.