You recieving any nude, sexually suggestive or her gratifying herself, photos is akin to her sending and you receiving child pornography. You sending the same to her is akin to child enticement, as well as a slew of other charges.
In either case with you being the adult, you will get the lions share of attention and jail time. She is after all, a child. No matter in your opinion how mature she may act.
Find yourself an adult 19 year old with whom you, an adult, can interact as an adult.
BIG SEXY says - "When life hands you lemons, take those same lemons & smash them into lifes' ugly *** mugg!! That'll learn'em to give you lemons."