Most Helpful Girl
Yeah I know exactly what you mean. It's best to keep quiet about your looks. If you are prettier than most of your friends they are very likely jealous and probably won't call you pretty. Not to sound conceited but I was with one of my friends and a few other girls we are friendly with (She's a bit closer to them than I am but I'm friends with all of them) and I know I am prettier than they are, but she was telling them both how gorgeous they are and how pretty they are, and not saying a word to me. The only thing she does is call me conceited for looking in the mirror, even though I don't say anything about my appearance.
Many girls hate to tell a friend who is prettier than she is that the friend is pretty, plus they assume the girl already knows it.
And if you put yourself down you do look like you have low self esteem.
I think it's best not to talk about your looks around other girls unless they bring it up first. If you know you are pretty that's what counts, and if you get guys there is nothing to worry about.