Waste of a girl.

My ex girlfriend is extremely beautiful and hella sexy. She has this cool rock star skater type vibe that most females tend to be drawn to.. And she's a drummer. We didn't work because she's a huge flirt.. But we still hang with the same circle and even though we each have our own lives, we are still protective over one another. . So there was a group of girls speaking (some we know, a few we don't) and she winked at one of them. I overheard them talking about how beautiful she is. Then one of the girls said "yeah she's beautiful. Too bad she's a waste of girl." I cut in and asked what was that supposed to mean she said "all that beauty is just down the drain and wasted." Basically saying , she needs to be with a man. My ex smiled and said "thanks". But it was such a rude thing to say. My ex is confident about who she is and knows people are ignorant so she doesn't let things like that offend her. But things like that annoy me so I couldn't help but say something and now my ex is annoyed at me telling me that I do too much. Do you think that it is rude to call someone a waste based off of their level of attractiveness and sexuality ???