Translation:She does not introduce me to her brother.
Excellent question! If both objects were pronouns, you could tell from the word order: ‘me lo presenta’ means “introduces him to me”, whereas ‘le me presenta’ means “introduces me to him”. But ‘me presenta a su hermano’ is in fact ambiguous, and could mean either “introduces her brother to me” (with the ‘a’ indicating an animate direct object) or “introduces me to her brother” (with the ‘a’ indicating an indirect object), depending on the context.
Yes. In fact, that's a better translation, because “introduce” is an action verb. Unlike the Spanish present indicative, the English present indicative is used only for the habitual aspect (“She never introduces me to her brother.”) and the historical present (“First she ignores my comment. Then she doesn't introduce me to her brother”).
mmm, well it's a little tricky. Anyway sometimes in Spanish you have to explain what you're trying to say regardless of how you intonate it actually hehehe, if I wanted to say She doesn't introduce me to her brother, I'd put a comma after presenta: Ella no me presenta, a su hermano (of course the sound of the comma would be a pause). She doesn't introduce her brother to me, I would say it without any pause. Ella no me presenta a su hermano.
In any case, I think the person talking should have to explain what is trying to say hehehe