Reaser joined the show this season as a sportswriter called Tammy, who is a possible love interest for Charles's character Will.
"I don't know how it all ends up, but I'm enjoying how they're writing it," Charles told Fancast. "It gives Will something to have on his own."
Charles also suggested that Tammy will be "here for a little while". She is expected to star in at least two more episodes.
The Good Wife continues on Tuesdays at 10/9c on CBS.