Interesting proposition, and they could possibly get her to leave for less, then CHANGE THE LOCKS. Have her sign something to show that she acknowledges their prior agreement for her to work for them has been terminated at the mutual concession of both parties.
Yes, I sort of left out the details but as you have stated it, is exactly how I would do it.
I found that the shock value of an even $1000 really got the tenant’s attention.
$300, No go.
$500, I’ll think about it.
$1000, I’m outta here.
And in the larger picture, $1000 was cheap as a last resort to get a problem to move on. I was sort of a win-win.