re: so the **** hit the fan, …
Kaam wali sounds better to me. Maasi sounds like it has a negative connotation, because of the way people talk about there maasi’s. We know their names so we usually don’t use either of them.
Kaam wali = someone who works(doesn’t sound bad at all)
To the OP
All kaam walis have their dos and don’ts but your MIL is a drama queen, there’s no denying that. My khala’s kaam wali washes the bathrooms whereas our kaam wali, told us she doesn’t do that, nope. That shows different kaam walis have different boundaries.