Well for one thing her eyes will turn 'blue' a few days before she sheds, her skin may also get kind of milky and dull looking. But you should know that already from caring for your other snakes?
As far as her musking goes in my experience this is perfectly normal for MBK's, as I have (had) a pair (my female escaped and is still AWOL) and the female especially has done nothing but that, rattle and strike since the day I bought her almost a year ago now. She is very bad tempered. The male isn't quite so bad, but he will also rattle and musk when held. They also seem to be excellent escape artists, so watch out for that. On a good note, I have heard of others here who have some very docile MBK's, in fact they claim that they're MBK's are the most docile snakes they've ever had.
Best of luck to you!
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"Klaatu...Verata...Nicht--cough, cough, cough!"