Forget all of this. Don't text her for a while. Just talk to her, in person, internet, whatever. Make sure she knows that her parents are overbearing and you don't want to get in an awkward situation, so keep the phone more private. Her mom just saw the text, likely she has no idea who you are. And, of course, make sure that it wasn't the mom idly checking her daughters phone, and assuming that some creepy pervert got her number off the internet or something.
Also, if something DOES happen between the 2 of you...well i'm sure the protection talk is pretty obvious, but also, check up on the local age of consent laws. In some places, it's possible for you to get a statutory rape charge for being 1 day older then the girl, assuming she turns 16 tomorrow, and you just turned 16 today. Make sure you know where you stand legally, and approach this maturely.
And no offense, but when you end your question with, "so wat do?", it makes a lot of people assume that you need advice in order to act mature. Text speak should be barely acceptable in texts, much less a forum where you have a keyboard.