If you are both under 18. Then No.
If she also likes it and gives consent , Then No.

Why would you send me texts to a girl?

Dude, are you crazy, I am on the verge of calling the Police on you right now and they will track your IP address and arrest you. Do you know how serious sexting is and how much trouble you can get in? Lol. Just kidding, don't be so cautious, just if she sends nudes, don't send them out cause if they trace it back to you you're in deep shit.

It is not illegal unless you get caught.

Dirty texts? Thats like 5-10 years.

lol our school had a cop come in and talk about it cuz it was happenin so much. He said as long as you don't distribute it it's not child pornography just don't send it out, cuz you can be put on the list of sex offenders. But texts aren't anything to be worried about.

If you posses a picture of child pornography, it is illegal, no matter how old. It is illegal to view, take/record, and/or distribute child pornography, no matter if your 15 or 25, it is still illegal.

What if you're say 15 and she's 15.
That's not considered child pornography/