Here's why:
* Subject Pronouns: These are used when someone is performing an action (e.g., "Alexia went to the store").
* Object Pronouns: These are used when someone is the receiver of an action (e.g., "I gave the book to her").
Since "her" is the object pronoun for someone named Alexia, you would use it in sentences like:
* "I saw Alexia, but I didn't talk to her."
* "John gave the gift to her."