Congrats on getting this girl to take a meal - hope it is all uphill from here. Hopefully you will be able to get her up to the size prey she was on with her previous owner now that she has settled in and is at least willing to feed. Brumation may help to give her an appetite too if she isn't feeding well for you after this. It certainly worked for a couple of ours (mexican milksnake and cornsnake).
I don't see a problem with intervening to assist with a shed - I have not had a snake go an extended period of time after being blue before shedding - most are within 14 days (max). When we have had to clear bits of shed off snakes (tail tips and such) I put them in a rubbermaid with a warm damp towel for an hour or so and they usually get it off themselves - no struggle, no hassle. I don't have mountain kingsnakes but suspect they might not want higher humidity all the time, so you might add a humid hide box when she does go blue the next time.
good luck with her - they certainly are beautiful snakes,