This happened to this poor girl, and literally millions of horrible things happen every year, because scumbag US politicians refuse to enforce our border laws. Because they want cheap, exploitable labor. And for much of the filth in Hollyweird and DC, because they want cheap sex.
There have been some ads posted lately (on public transit, and elsewhere) in my general neighborhood warning about human trafficking and how most trafficked girls under 12 end up as prostitutes, and another print ad campaign warns that underage prostitutes are rape victims. The people supporting "amnesty" also, curiously, oppose human trafficking and all the ills it brings.
Someone out to buy sex isn't going to check a girl's age, or check her legal status.