Is mom a subject pronoun?

No, the noun 'mom' is not a pronoun.

The noun 'mom' is a noun, a word for a female parent; a word for a person.

A pronoun is a word that takes the place of a noun in a sentence. The pronouns that take the place of the noun 'mom' are she as a subject and her as an object in a sentence.

Example: My mom made the cake. She bakes a lot. I will tell her that you liked it.

The noun 'mom' can function as the subject of a sentence or a clause, and as the object of a verb or a preposition.