It's what i wear so why do they care?

so the shirts i wear are low cut, but i wear an undershirt w/them everyday. its nvr been a problem until recently some random person went to my formspring and said my shirts are too low cut i explained that i wear undershirt and to not worry about wat i wear. well then they said some other rude comment. the thing is i have big im not going to wear a shirt that goes to my neck bcuz then i feel like i cant breathe. i make the shirt less low then it should be and tho the guys dont mind my shirts they actually like them the girls need to stop. what i dont get is why they feel the need to talk **** about me. i dont flirt w their bf's or hangout w them bhind their backs so i dont get it. i nvr had a problem with it until ive been bugged about it over and over again recently. im not going to change for other ppl i like how i dress and everyone that knows me knows im not a slut. so why do u think the girls talk **** about me wen i do nothing wrong.?