Why "she don't" doesn't work: a grammar breakdown

What kind of error is it?

Subject-verb agreement error

Why do people make this mistake?

The error often occurs because "don't" is widely used as the negative contraction for "do not," and some people mistakenly apply it to singular third-person subjects influenced by informal speech patterns or dialects.

What is correct?

The correct form is "she doesn't" because "she" is a singular third-person subject and requires the auxiliary verb "does" to agree in number.