I am with you on the tragicness of such fashion sense but on the other hand unless she asks for your personal opinion you should not say anything. She is your friend and if she is comfortable it shouldn't make any difference.

That was the ethical side of me. Now the other side of me says damn I would probably be mortified goin out with her (I know that is shallow). If some how she could see that clothes that fit are more flattering than looking like strung roast. Some sort of enlarged photo of her in the offending outfit.....
How did that get there ? you would say