Of course not - I think alot of girls look really cute when they are tom boyish - baseball cap, pig tails.
My older daughter is very tom boyish and she is beautiful. She loves to dress in comfortable clothes and loves sports. Actually many tom boyish girls are in better shape as they are very active. And boys always have a crushes on her - when she tells me this - my response is - you are smart, pretty and love sports - what else would a boy want?