Hey Chinabun,
It's actually okay for her to lick at the wound to help it clean itself. We recently had a rabbit with very deep, very nasty wounds on his back- they were infected. We would put ointment on the wounds and let him pick at them to his heart's content after making sure the ointment sunk in, and he wasn't licking it off. It was about as extensive as yours is, although he didn't transfer any kind of dermatitis, which is probably how hers got a fungal infection on it.
So yes. In my opinion, she shouldn't have the E-collar on constantly. This will hinder her cecotrophy- the eating of cecotrophs, or the "special packages" of poop that rabbits need to consume in order to really be able to eat properly. If you feel more comfortable having the E-collar on all the time, try to pick up her cecotrophs and let her eat them. They are the smelly, soft poops that look like little bunches of grapes, almost. They're pungent. You can't miss them.
What *I* would do, personally, is put the collar on before you put the ointments on. Let the ointments sink in for a few hours, with the collar on. There are antibiotic ointments that also have anti-itch properties, perhaps one of those would be a good thing to get. And after a while, I would just take it off for a few hours.
You could also try putting some of the Keto on the lump on her jaw, in case the dermatitis is caused by a fungal agent. What I would think, is that the skin problem on her jaw lump is caused by a fungus, she got an open wound on her back flank, and began grooming it. The fungus got transferred. But luckily, the medicine will help with that issue!
Best of luck to you and Qingqing.