to answer your original question: Yes I have. I know exactly the kind of girl you are talking about.
first off, i cannot say i would feel threatened by guido-the-pimp, unless he managed to trap you in a dark alley. their business and livelihood depends on staying off LE radar. they won't mess with you, as they would with other street people. losing a potential profit machine means little when going after you could easily end up bringing his whole world down. its annoying to lose someone who you spent the bucks for a protein bar on, but as easy as it was to get this one, there will be others.
second, you don't have to tell us she's not too bright. the fact that she would follow his reasoning and stick around to turn tricks for him because she's afraid of him or because he has her favorite pair of boots at his apt tells us all we need to know. there is very high demand in this world for gorgeous-but-stupid girls, both among low life pimps and the rich and powerful. she just had the bad luck to have the former notice her before the latter. these girls are a hot commodity, and it is a fine line between whether they end up street whores or some rich man's 2nd wife. i also know she is not necessarily "not too bright" intelligence wise; what we are talking about is a lack of wisdom, common sense, and extremely poor judgment.
you could/may have saved her. it is winning the battle. her poor judgment will have her in jeaprody the rest of her life. hopefully she will be luckier with the next one that takes a shining to her.
it doesnt sound like you are inclined to make saving her one of your hobbies...sounds like you are just enjoying the fruits. all the more power to you. if you do start changing your mind, be aware that you would be taking on a huge job and headache for a long time to come.
And with that caveat in mind...enjoy. btw, these girls also tend to run in packs, so keep an eye out for her friends...
...and if it comes to pass you have you hands full with too many fuck buddies, please send the overflow this way