Have you been adding reptile probiotics to her food, after being on medication for infected scent glands? I sure would. It might be that she is feeling stomach irritation as "hunger" & let's face it, some king snakes are "eating machines" anyway- it doesn't take much for some of them to chase their tails (or their owners, lol).
I'd also stop using those wood chips as substrate, just in case she's swallowing some.
Does she have a big enough water bowl to bathe in? When she bites herself, what I'd do is quickly put her in the water bowl- it won't hurt anything but should "change the channel". Water spray was too subtle for this king snake, obviously. She does sound like she has a hyper-active prey drive but I hope you can calm her down- I'd not want to see any snake of mine doing this either.
I've only had one snake* that ever bit their own tail- it was an elderly albino cal-king, & she only did it once. She seemed a bit senile att, & she passed away about a year after that.
*Another was a w/c turned over to me- sadly a brief acquaintance- a longnose snake that suddenly kept biting itself & then died quickly- apparently from parasites from their herp diet in the wild.
You've done everything possible for this snake, it's not fair that you've had so many crazy issues with one snake, & now this again? What an ordeal.