As the MC is presumably Indian by her skin color in the first few chapters, I’m guessing the meaning of “untouchable” relates to the caste system. The old (it was ended legally, but the people still mostly follow it) Caste system of India splits into a bunch of different levels, but the “lowest” level of the social pyramid is actually not the real lowest. The true lowest caste is a caste outside of the caste system itself, the “untouchables”, usually given dirty jobs such as graveyard keeper or toilet cleaner.
As the MC is presumably Indian by her skin color in the first few chapters, I’m guessing the meaning of “untouchable” relates to the caste system. The old (it was ended legally, but the people still mostly follow it) Caste system of India splits into a bunch of different levels, but the “lowest” level of the social pyramid is actually not the real lowest. The true lowest caste is a caste outside of the caste system itself, the “untouchables”, usually given dirty jobs such as graveyard keeper or toilet cleaner.