You could have just sealed it right there if you want to be in a relationship with her...
her: you're good and i want to be with you for a while
me: I suppose you're in then. Probationary status only
Face to face - way better... I'm surprised she would do that over text, but I don't know your ages... Maybe she's more comfortable with that shit.
If/When she brings it up in person, take the same approach and play it to the situation -- like the example above (though that one may not fit, depending what she says).
If it's what you want, all you have to do is say yes. You're playing it like someone who doesn't want that.