Good question. I think as I'm rereading this from the beginning, cuz I need to catch up and figure it was going on, it was because she never had a chance to. She was isolated and shamed into being on her own. She didn't think her family would care or that it would prove she was incapable. Also remember that the Mother-in-law was keeping her isolated and taking money from her so she probably blamed herself for that too. Basically she was gaslit into being obedient and then that of course led to her downfall. I'm sure if her sister knew, or in the past if she had told her sister was going on, she would have helped. Basically it was just a domino effect
She didn't ask for help and left after an argument, so they thought she didn't wanna speak to them and she thought they wouldn't help since she always felt second to her sister
Why did her family never helped her in her past life?