There are good advices by T-mal & artandale..
But for me, which I don't favor of long text-game, I will prefer to ask the girl out as soon as possible.
As for your case, did you find anything you like, such as her favourite food / drink?
THen invite her to a place that serve her favourite food / drink..
Or I will just tell her ,"it's fun texting with you, but I am not sure is it fun to talk to you over a meal (or drink) too? will you willing to solve my curiousity I am free at tuesday night & friday night, which is a better time for you?"