depends on the context. from someone in my peer group, used in a casual and friendly way--wouldn't bother me. though i don't think any of my friends use "girl," we tend to say "hey woman" instead *shrug* in this sense, i'd view girl as the female equivalent of guy.
and i don't care what word someone uses, i don't like being talked down to period.
i despise terms of endearment from strangers--hun, sweetie, baby take your pick there are tons available. when someone uses girl in that sense, i will correct them. i get this a lot from people at work (not coworkers, but patients) and i do tell them i'd appreciate it if they called me by my name. i don't refer to them that way, i expect the same respect.
the only time i actually smile when being called girl is when it comes from my dad. not often, but sometimes he'll refer to me as his girl, his little girl or his baby girl and i gotta admit, the child in me loves it
though generally this occurs during those moments when he reflects back on how much i've grown up. i think it's nice. he respects me as a woman, but in his heart's eye, he will forever see me as his child. to me, it's a bonding phrase.