Ji-Suk herself is a representation of what it means to find balance between honoring tradition and being unique. When she was younger, she did as she was told and lived by her mother's standards and traditions. Ji-Suk is the American daughter if a Korean woman. She was "forced" to take Korean and violin lessons, as well as to cook Korean delicacies. That was her mother's way to have her daughter be more Korean. Such rigidity in her demands is a reflection of her culture.
However, even though the mother wanted her daughter to develop her Korean side, she also wanted her to succeed by American standards, which she thought meant going to college and becoming a lawyer. After her mother's death, Ji-Suk is finally able to find her own balance. She is no longer a lawyer, but is still successful as a food truck owner. She does not feel less American or Korean for choosing to do so, she actually believes she is honoring what her mother taught her. And she is happy! She has also learned her lesson: she won't do the same to her own kid. She will wait for him to find his own balance, which seems to start happening at the end of the story. Seo-Jun chooses to stay and help her instead of going meet his friend. Maybe in the future he will even develop a curiosity for his mother's culture and traditions; he seems sensible and sensitive.
The answer b states that "from then on" meaning her behavior has changed toward her brother and the passage states how she has been putting a little extra thought into how she interacts with her brother.
Someone with a heritage language may have difficulty learning English because they were not born into the language. People with heritage languages have different ways of spelling and pronouncing things. If someone who spoke English tried to learn a foreign language they would also have a hard time grasping the language too because of the spelling rules and how they pronounce their words.
