That might be something that happens on your main playthrough, but it does not happen on mine. It becomes very clear from early on that Lena´s Mom pretty much prefers her son over her, treats her like a servant and misuses the money sent by Lena.I'm not getting it from the story at all. Lena's relationship with her mom is strained but it's because Lena thinks her family doesn't understand her passions, and she dislikes how her mom never changes her mind based on other people's advice.
Lena is currently sending money home because her mom is no longer employed and can't find another job, between her age and having no higher education. But it's pretty new development, at the start of the game Lena mentions in a talk with her that they still have savings from mom's former job and bakery sale. And if anything, her mom feels guilty it's her daughter supporting her financially and not the other way around like it was the case before.
That she is the fifth wheel in her Mothers eyes becomes pretty much certain during her talk with the stepdad, who is the only one in the family treating her decently.