Text her something simple, and make sure to put "-Ash" at the end so she can't reply with "Who's this?". Use callback humor from when you got her number. I'd say exchange no more than 3-4 texts before texting her, "We should grab a bite to eat, what's your schedule like this week?" Or any variation of that, pertaining to whatever it is you want to do with her. Don't prolong the text conversations, texting is for setting up meets. If she wants a texting buddy, it isn't you, leave that for the chumps who aren't bedding her. Don't be any of the first three stages of AFC when it comes to texting.