CAN they look at them? Yes. Are they allowed to do so? No.
There is one thing that I was taught some years ago by my then boss. It was applied to e-mail back then, but I think it should apply to all digital means of communication now. He told me to never send an e-mail that you wouldn't want the whole world knowing about. Once you release that data into the wild you have no idea where it will end up or who it will end up with. I believe the same applies to texting, forum posts, digital pictures and so on these days...
Now I have no problems with you sexting with your girlfriend. Jjust remember, NOTHING you put out on the web or any kind of wireless network is even remotely private anymore. everything is recorded, copied and saved to a database somewhere. That means that some, either legally or illegally, can access your information for whatever means they desire.