After defeating Debilitas with the chandelier, doing so will make it seem that he was killed, but then he will recover and then see her silhouetted through the church window, and bow to her.
Ending A. Debilitas simply bowing to Fiona and allowing her to leave the castle.
Fiona and Hewie's relationship is a heartwarmer, in general. Here's some moments that can put a smile on your face.
After Fiona saving Hewie for the first time, he later comes back to save her from Debilitas.
In one of his comments, Hewie mentions he loves (What he considers) playing games with Fiona.
Hewie keeping Daniella from attacking Fiona before Daniella's boss battle.
When she finds Hewie shot, (Which was obviously the work of Riccardo) Fiona bandages him up and as mentioned in one of her comments, she decides to let herself get chased by Riccardo so he won't kill Hewie while the poor dog is defenceless.
Hewie saving Fiona once again when she was locked behind bars. If you look at Hewie's comment here after hearing the cue for a new one, the latest one will mentions he was looking all over for Fiona.
After defeating Riccardo, Hewie says in his latest comments that he (Hewie, definitely not Riccardo, of course) and Fiona are soulmates.
In Ending A, B or C, Fiona appears to be frightened when she tries to put the key into the door that will lead her and Hewie out of the castle. However, she calms down when she hears and looks down to Hewie, letting her unlock the door, calmly and exit the castle with him.