While it’s not hard to see where Mr. Fitt is coming from given the dire (my attempt to go historical) financial situation of the Philadelphia Fitts, it’s also clear that for Mrs. Fitt keeping up appearances for the society is more important than happiness. She is not alone in wanting Eleanor to be who she wants to be because doesn’t everybody’s parents at some point (especially those of the 19th century!).
It is complicated because she seemed to have given up on Elijah to look after the family so she focuses on Eleanor; keeping tabs on her, dressing her up to make her look more appealing, forcing her to spend time with the richer members of the society and what not. This sounds so much more appealing and easy than losing their home, social status and money once and for all. Looking at it from this point of view might justify her demands of Eleanor but keeping Eleanor’s opinions and emotions in focus becomes impractical this way. Eleanor does what she can to dodge her attempts at conforming her according to what the society will or will not find acceptable.
I’d like to point out here that Mrs. Fitt is not one of those haughty parental characters who cast a jaded eye towards their children’s well being. She does care for Eleanor but it’s clear that she places more importance on how society looks at the Philadelphia Fitts. However, her approach is definitely unjustified and infuriating. But given the time period, I’d say it is justified because that’s what used to happen in those times.