If you can't persuade Buttons, the only option to continue is to kill him/her then dialogue comes up allowing the transport of the girl to the ship. It sounds like there is no difference whatsoever other then Buttons survives in undead form. Too bad you can't transport both of them. I think she'd have a hard time passing the death fog in her cat search - she probably never learned how to use the source very well being so young. I'd like she did reunite, perhaps Buttons sensed her near and crossed over himself (walking on the bottom of the lake or whatever).
As far as I know, there are no sourcerors on the north of Bloodmoon Island. It just mentions one on the magister bulletin board there and the only character of sorts on the north of the island is the dead druid so I guessed it might be him. It's possible something was planned for there that was never done too plus, in a game like this, I'm sure there's still a lot that I missed.
