T.F.
That is a toughy. Questions are how old is your daughter? What type of site is her pic on? Is she is a minor? Do you know who she shared these pics with? If she willingly shared pics with someone you may not have a lot of options. As we all know, any pic can be copied and used elsewhere. Whomever she shared the pic with might have shown it to someone then there you go, it is on the WWW. You may have a lot more ground to stand on with these questions but NOT if she is of legal age and shared the pic. It is a common mistake a lot of people make. Usually, once on the internet, it is there for good because is gets passed, copied, posted, etc. It gets out of control.
Contact the website administrator where the pics showed up on and let them know pics are stolen. This actually happened to me once. My pic was not nudity but very sensual and it was on a site advertising for something I am certainly not interested in. We contacted the website admin and it was gone within 12 hrs. We did threaten to have a lawyer stop the website as well. I am not so stubborn to know that the pic that was taken down of me might be somewhere else.
Now, ANY pic I have has a special code on it so IF it gets copied and posted anywhere else, it is coded and known that it is stolen.
I don't know what police can actually do UNLESS she is a minor. It is a whole new ballgame if she is a minor.
I hope something I said helps.
tf