I had a similar experience here, but I could defend myself using my feminine voice. I did ask them if they could repeat what they just said as I didn't quite get it as it did sound to me like she was suspecting that I was a guy which couldn't be true at all. That made them running pretty fast.
Not sure what such girls want or do - I would see quite a lack of self esteem on their side that they feel the need to wreck someone else's day.
But let's face it: they wouldn't have talked about you if you wouldn't have looked great.