How do i tell her? PLEASE HELP!!! ANYONE?

my friend has really bad fasion sence. its not that i care about fasion but she wears the wrong clothes for her body and it looks bad and sometimes dirty. shes so prettty but she creates sucha bad image for herself. dont say 'thats just he style deal with it'/ coz its not she trys so hard to go for those style but gets really unflattering things. how can i tell her subtly without herting her feelings.