From there, they were transported to Egypt, where they were smuggled close to the border and "conditioned". Conditioning involves repeatedly forcing them to take strong drugs like heroin, so that they become chemically addicted. The drugs act as an effective restraint. If the girl escapes, she has no way to get a fix within 48 hours, and goes into withdrawal.
Eventually, they are smuggled into slave markets in various countries there, where they are auctioned off or sold via direct sale. Usually, an auto mechanic is involved - he will build the girl into a car for transport. She will be sewed into the seats in the back of the car, built into the dashboard just behind the engine - it's simply awful. Travel can take several days and many don't survive.
I can't say much about how we intervened, but we worked with the authorities to intercept them and repatriate them to their homes in Europe.