Yeah, just ask her out. She likes you, that much is obvious, so its only a question of how much. Enough to go out for a drink with you is a good sign, if she says yes.
I know nothing about you, despite what you post here, and nothing whatsoever about her, so its up to you to make that move. If you're paralysed with nerves at the thought of asking her for a drink, then perhaps just tell her that. Be yourself, as she likes you anyway, a quarter of the battle's already won.
And buy a new shirt and new underpants for any date that may arise. That is very, very important.
I don't know, what with this and peter wolf's recent posts, im rubbing my hands together in anticipation of an uncoming thread of 'bumsex girl' proportions!
SBT