Daughter not wearing underwear etc. Help?

My 9 year old daughter was about to get in the car... Before she got inside the car she slipped on a puddle, her skirt flipped up a little and i noticed she wasn't wearing any underwear. Is this normal? Also another time I caught her not wearing underwear when we were at a restaurant.. And on a few other numerous occasions. I've also seen her watching porn sometimes, when she sees me watching her, she quickly exits the website. Whats happening to my little darling? Is this a natural thing to happen to a 9 year old? Please help :(