Is "She don't like spicy food" correct?

Why

Riya has learned "don't" as a general negative helper word, and hearing it used constantly in everyday speech ("I don't", "they don't", "we don't") makes it feel like a fixed, universal word. English actually splits this helper depending on the subject: "I", "you", "we", and "they" pair with "don't", but "he", "she", and "it" — the third-person singular subjects — pair with "doesn't" instead, matching the same third-person-singular "-s" pattern seen in "she likes" versus "I like". "She don't" mismatches the subject and its helper word, the same kind of clash as "she go" instead of "she goes". Test: line up the pattern — "I don't run", "you don't run", "he doesn't run", "she doesn't run" — the switch happens exactly at he/she/it, nowhere else, which is worth memorising as one single, predictable switch point. Her brother is right: "she" takes "doesn't", not "don't" — the helper word has to match the subject the same way any other verb does.