Answer :
Since Melissa is one person, and we're assuming she's a girl you want to use "her." Melissa decided not to sell her sofa.
Unless the sofa belongs to someone else, then we'd use something different.
If the sofa belongs to one man = his
If the sofa belongs to a group = their
Unless the sofa belongs to someone else, then we'd use something different.
If the sofa belongs to one man = his
If the sofa belongs to a group = their
