No -- she obviously doesn't have compunctions about reducing your hours (and income) as your employer -- just being a little in your face to make you realize their are two relationships on BOTH sides.
If you get the job and agree to accept it, then tell her and give her adequate notice.
I think people often think they are completely irreplaceable in terms of giving notice (not saying that you are) but in every work situation I have been in employees come and go -- sometimes their replacements aren't as good or I haven't had the same relationship, but in the end, the work gets done.
Some days I pray for Silence, Some days I pray for Soul,
Some days I just pray to the God of Sex and Drums and Rock 'N' Roll.