Factual error: At the beginning Scrooge is seen signing Jacob Marley's death certificate in the year 1836. English Birth, Marriage & Death certificates didn't come into being until 1837.
Continuity mistake: In the scene when Scrooge is talking to the boy after he changed, the boy has a sled that was right by some posts, but after Scrooge gets excited because he didn't miss anything and we go back to the boy, his sled is now further away.
Revealing mistake: During the scene when Scrooge is sitting in his armchair by the fire, the animation of the fire is badly looped and you can see it flickering as it finishes a cycle.
Answer: Yes. He promised to marry her and she's releasing him from that promise, as she realises he is no longer really in love with her.
Brian Katcher