After Leslie dies, May Belle the only one who worries about him being lonely, telling him, "I just wanted to find you, so you wouldn't be so lonesome" . When she tries to follow him into Terabithia and gets stuck on the makeshift, tree branch bridge and really puts her life in jeopardy saving her is something that brings Jess back to himself and helps him realize more important lessons Leslie taught him. May Belle shows Jess he's still loved and needed even after Leslie's gone, and makes him see he can still get to Terabithia. It seems like he makes a real, proper bridge across to Terabithia so that May Belle can go there with him too. In teaching her to see Terabithia for herself, he's reminding himself of how to see it as well.