When does a indefinite pronoun function as an object of a preposition, or a direct object.?

Question

In the sentences, "Mary brought everybody cookies." and "The girls are washing windows for someone." Are the indefinite pronouns direct objects, or objects of prepositions?

Answer 1

The second already has a preposition to serve the direct object ("for") and "someone" is the indefinite pronoun. The first sentence does not have any prepositions and "everybody" is the direct object. Prepositions and indefinite pronouns are different.

Answer 2

Object of a preposition: it follows "of, by, for, on, over", etc.
Direct object: What the verb is done to

Mary brought the cookies to everybody, right? So it follows a preposition.
The girls wash windows for someone, follows a preposition, right?

As opposed to: I saw her yesterday. "Her" is the direct object.

Answer 3

They are direct objects because they follow a verb. To be objects of preposition they would have to follow a preposition such as in, on, at, of, above, with, etc.