Well, text is easier on yourself, but it kinda makes you look a bit funny, if you know what I mean. If you want to talk to her, why not use the phone?
Of course, I wouldn't no any better since I lack the balls to confront girls. Yet I still think you should try the phone. If you're still too nervous about it, then get yourself a bit tipsy and set your mind "on the level" before you dial. The hardest part should then be more easy to take care of and the slim chance of a rejection won't be as bad.
But like I said, I wouldn't really fucking know any better.