Maggie attempted to leave the watch with Glenn’s grave, but Gregory’s greed almost ruined that, and it was after busting the leader’s chops for his thievery that she referred to herself as Maggie Rhee for the first time.
Back in Season 2, Hershel gave Glenn his family heirloom watch, which the younger survivor kept close right up to his death-by-Lucille in the season premiere.
That’s something she wasn’t able to do in the source material, as Glenn’s surname hasn’t been revealed.
(Glenn was actually wearing his baseball cap when Negan killed him in the comics.)