This was a weird situation I was in and I'm not sure if I should have reacted differently.

I take a water aerobics class and most people sit in the large hot-tub afterwards. There is a swim clinic for kids a half hour after our class ends, so there were 5 adults and two kids (waiting for class to start) in the hot tub (it's huge!).

A girl (I assume 9-11 years old) walks in and before she even gets down two steps a woman in my class asks her "Are you mixed?" without saying anything else. The conversation went like this:

Woman: Are you mixed? (in a very neutral tone, not overly friendly or rude)
Girl: Uh, yeah (really shyly)
Woman: Like what? (Implying what are your parents' races)
Girl: *questioning look*
Woman: Like are you black heritage and white heritage, or hispanic, you know what I mean?
Girl: *mumbling* (I couldn't hear what she said)
Woman: Well your hair is pretty. Usually you see either black hair or white hair, and your is very much a mix of the two. It's very pretty.

I was sitting a little ways away, so I scooted over and then engaged the girl in conversation because I could tell she was uncomfortable. I asked her when her class started, if she gets cold going from the hot tub to the pool, what they are working on today. She was talkative and told me about her class. The other woman left, and then I got out and told the girl to have a good class.

It was an awkward situation and I wonder if I should have said something to the woman. I've faced blatant racism before and had no problem speaking up, but I couldn't think of anything to say in this situation.

Am I making a mountain out of a mole-hill? We are planning to adopt in the future and there is a strong possibility we will have a interracial family, so maybe I'm hyper-sensitive to these types of encounters.

What would have you done/said in this situation?