Quinn's criminal empire is extremely poorly explained, so we can only speculate. That said, it's pretty clear that it may operate within the HOTs, but it is not the same as the HOTs.
Quinn planned to add Camila to the restaurant from the start, so she started working as soon as she pledged. Maya and Mona look like later additions, as the first indication Quinn was considering adding them to the restaurant was in Episode 3 in the pool scene, where Mona leaps at the chance for free tuition and Maya equivocates. Prior to that Mona isn't really mentioned and Maya seems to have been more about making her behave in degrading ways. It's possible Quinn thought that would be a good way to coerce Maya into the roll, but it's also possible Quinn decided to expand once she realized she was going to come up short.
My guess is that Quinn is either confident Mona will be accepted (she did create their list, after all), or would be willing to keep Mona in the racket even if she doesn't make it into the HOTs. So Mona was given an 'official' assignment at the ANO party (which then went sideways). It's less clear what Quinn's planning for Maya, but my guess is that the reason Maya had all those sexual tasks was so Quinn would know if she could really go through with it. So she's holding off on informing Maya about the restaurant until Quinn sees how she handled the scavenger hunt.
Lily, Ashley and Josy only pledged the HOTs halfway through Hell Week, and it's still not clear if they are going to be added to the menu. The way Melanie and Sarah treat Lily and Ashley in the sauna could be an example of grooming the new daughters for it, or it could be the two HOTs indulging their crueler side. Josy is even less clear. My guess is Quinn only accepted her to tweak Tommy, and Quinn has no plans for her beyond that. It's a bit hard to square that with partnering her with Maya, but that may have been unavoidable.
Now, IMHO all of this is pretty stupid, but then again, that's exactly what Riona says to Quinn. It seems clear that Quinn isn't actually all that good at running drug and prostitution rackets. Perhaps she only got this far due to luck, or maybe she inherited her empire from another sister that graduated. But whatever the case, Quinn is in over her head and getting deeper swiftly.
We won't know if this a fault with Quinn or with DPC's writing (or both) until we learn the backstory.