Teenage daughter problems, What would you do?

My teenage daughter has been texting a LOT, and i mean A LOT of boys lately. I'm not one to be nosy, but this was urgent. I went through her phone while she was away and some of the texts were disturbingly ual. I don't know how to confront her. I'm concidering taking away her phone, but at the same time, I was the one who went through her phone and invaded her privacy. Normally I would'nt mind if she was texing boys, it's all part of growing up, but a few of the texts were ridiculously graphic and I have no idea how she even knows some of the things the boys were saying to her. I don't know what kind of punishment to give her... What would you do???