I think the movie is from the 1980's. A little girl is dreaming about a monster that only eats pictures of flowers. At the end she wakes up singing a Christmas song, I think.

The Monster's Christmas (1981) — A young girl helps the monsters from her storybook defeat an evil witch that has stolen their voices because they sang better at Christmas carols than she did.

I had been looking for the answer to that myself for quite some time.. all I could remember was there was a little girl with a monster who ate pictures of flowers.. I have to see it again even though I don't like Christmas movies.. just because I have had a very old memory of it my whole life. Nostalgic purposes