My grandmother happily presented the family heirloom at the wedding.

In this sentence i believe heirloom is the direct object, presented is the verb but i need to know what the subject modifier is and is happily an adverb that describes presented?

Yes, "heirloom" is the direct object and "presented" is the verb.

The possessive pronoun "My" modifies the subject.

And -- "happily" is an adverb describing "presented."

To determine the subject modifier and the role of "happily" in the sentence, let's break it down:

Subject: The subject of the sentence is "My grandmother."
Verb: The verb is "presented," which is the action that the subject performs.
Direct Object: The direct object is "the family heirloom," which is the recipient of the action.

Subject Modifier: In this sentence, there is no subject modifier. A subject modifier is an optional word or phrase that adds extra information about the subject, such as "smartly dressed" or "always cheerful." However, in this specific sentence, there is no additional word or phrase modifying the subject "My grandmother."

Adverb: "Happily" is indeed an adverb in this sentence, providing additional information about how the grandmother performed the action of presenting the family heirloom. It modifies the verb "presented" by indicating the manner in which the action was carried out – in a happy or joyful manner.