Is it better if we stay like this or if I ask her out?

Well if I were her, I wouldn't want you to just like abandon her all of a sudden cause she's moving. But don't make long term plans, because it will suck when you guys can't hang out or talk and you don't get along so well. So just enjoy it while it lasts, talk frequently and hang out as often as you can- make it as cool as it can be when it is, and then when she leaves just give her a goodbye kiss and except that things don't last forever.