when can Anna be made a whore?
Make sure she's on the Slut route and keep leveling up, when you reach five hearts, it should lock her route, there are a few events that happen before then, once you reach that stage, a lot of options will be available to you (If you take Anna to Starcon three times, you can unlock outside shoots, for example. If you paired Ken with Samantha, you can eventually run into them at Starcon and you can suggest swapping mothers, depending on your decisions with Celeste and how that arc ends, you can call Celeste when you go to Starcon and have a threesome with her), I think taking her out to the park is a good indicator of your progress as well, she'll eventually run into strangers (As far I have discovered it's two strangers, an unknown man, and Jeff, an old high school classmate of Anna's) that you can pretty much pimp her to (Or have them get with her for free). So in other words? Keep her on the slut path and keep leveling up. Hope this helps!