A doctor has pretty much seen it all, due to the fact that they are doctors they tend not to get embarrassed by that.
Because girls are growing up. It is natural but it is unknown to them. I think embarrassed is not not the right word/
Most possibly most classrooms have a toilet bucket so go in the bucket. Boys and girls would be embarrassed because you'd have to in front of boys and girls. Why its embarrassing if here nothing to cover you every one would see your private parts.
I may not be able to answer this question from experience, for I am not a female, but i would say no. You do not need to be embarrassed about it. I am openly pan, and have had no problems with it, nor have other people. If girls are your gig, then go for it. You should not be embarrassed about the way you truly feel.
They're embarrassed because if they know other girls have bigger boobs than them, they feel like the girls that have bigger boobs are better and more attractive than them. If that's not the case, then maybe they think their boobs are too big. I don't know... You shouldn't be embarrassed about how big your boobs are. 
He prefers that girls are smaller than him, otherwise he feels embarrassed.
yes, because girls mostly like taller boys!
They love you, they're embarrassed, or they're tired
Because she's too shy and embarrassed. Some girls are like that.
There is no way to know what percent of girls finger themselves. Many girls would consider that private and an accurate poll is not very likely to happen.
Their private
because they are to embarrassed to say no
they do private stuff