Agreed
Ya know....that was easier said than done. What's the alternative than trying to trust the uncle? Both of them think about each other. The FL didn't want to worsen her auntie's condition (although that was a failure) and the auntie didn't want the FL to work to fatigue.
In a way, they are helpless but definitely not dumb.
They actually should have known better or be more suspicious since they actually know the history of that bad uncle.
The thing is IRL women in this situation have the capacities to free themselves, if they have the guts and intelligence. No rich ML came to rescue them.
Just don't forget in which time period it was written. It was probably situated during the 50's to 70's and the women didn't had so much choices...
That story would be more empowering, if the FL and her aunt wouldn't be so easily manipulated/blackmailed by that Uncle and his wife.
I like that the ML isn't our typical Alphahole but I find find quite unnatural that he suddenly became a knight in shiny armor when FL suddenly became dumb and helpless.