"because" only has one meaning, which is to introduce a reason. So here, it is a reason. However, your doubts are a sign that you understood the meaning well because it is a very strange sentence: it is not at all obvious why sitting on top of the chest of drawers would make her the most elegant doll. However, if you changed the sentence round, it would sound much more credible: "She usually sits right on top of a chest of drawers because she is the most elegant doll." My conclusion is that the writer is not a native speaker, that he or she made a simple mistake with the order of the sentence, and this unfortunately changed the meaning completely.

For me "because" is correct-right in the sentence. It's just "most elegant doll" cause is on the drawers