Actually
motseer I'd guessed how you meant it but it was easyer to explain why it didn't seem appropriate useing the Do association.
The Dom aspect unfortunatly is what Mistress is associated with in most societies these days.
But I used that to try and point out that Mistress would be out of place in the Fox Box.
Other times Mistress makes sence can be
She is a Private School governess.
She owns slave's.
And occasionally she's an odd stuck up bitch with a superiorite complex that happends to employ servants and will insist on it.
Otherwise it is not normally used in any other profession that I can think of atleast not these days.
And although I used it as an example of a more fitting tittle for Fox Box given how Tracy treats the girl's.
I disagree with the can't use it they allready have a Mamma Della argument.
Even if they already call one matriarchal woman Momma out of respect.
It is just as reasonable an assumption is it not? that they are just as likely to be inclined to call another motherly female they respectand and is their boss.
Also somthing like mom or momma and then to differentiate it by possibly calling the lessa of the two hierarchical women Tracy.
Something like Momma T when they are together with Della and Momma Tracy when Della isn't around?.
Pesonally I wouldn't call my female boss mistress unless it said I had too in my contract.
I have called one Mom before.
But then I was friend with her kids before I worked for her and used to call her mom when I played at their house.
She was not best please'd to start with.
Especially when some of the others started copying me by doing it too.
but after she realised we were doing it out respect and not just taking the piss.
And didn't call her that while she was dealing with her collegues and bosses she evenchally started to enjoy it.
But thats just my opinon on why Mistress don't seem right in this case.
P.S. of corse in a bedroom enviroment and wearing her Fox Box uniform Mistress can work
But I think Miss Tracy works better like "come here a moment Miss Tracy and take some Dick...tation" .
Disclaimer: this is still strictly only my opinion.