Heh, not only is your statement wrong on so many levels, your question is wrong, too.
1) Grammatically, your sentence is fine. Your meaning would have been more clear if you had said, "I like the Christmas tree more than I like her," but your sentence as it stands originally is not wrong. Grammatically.
2) Etiquette-wise, on the other hand, it just wasn't nice. Even if it were a joke, it was not a nice one.
3) ...and the problem is, it wasn't a joke because as you say in your post, you don't like her and other people, picking up on this vibe of not liking her, probably took your statement as more truth than farce which is why they assumed that you really are attracted to Christmas trees.
4) ...BUT the biggest problem of all is that you do not understand that making jokes about not liking people is not nice and tried to 1) gain support for your sentiment here by 2) attributing the misunderstanding to poor word-usage instead of to poor taste. Double-not-nice. Even if she were someone disliked by many people, it's still not nice to make fun of her.
Overall, just not nice.
Shame on you. 'Tis the season.