12 yr old slut rumours

I have been hearing alot about 12 year old sluts.My sister is 12 and she is very honest with me as we are very close.She has told how she has a boyfriend and has kissed him but alot of her friends the same age have in fact had sex with their boyfriends.I feel that this is VERY inappropriate I thought that when she had kisses a boy at twelve( I was 14 i had my first kiss) that was something big I'm mortified to think of how many girls could be pregnant at 13 years old.Also girls in the age group 11-14 have started dressing inappropriately as they feel that their old clothes are to babyish and they will get teased so they are going to places such as supre and other places which is causing them to look like little sex objects that are really just girls trying to fit in.