I'll warn you that I'm trudging into mild/vague spoiler territory, if you'd like to stop reading:

The book was quite effective at making her plain. In fact, when she's introduced I think it's just to show what a douche the main character is and I didn't think more about her. Imagine my surprise when she shows up like thirty pages later. And I'm fairly certain there is not transformation on her part, though I will say that since the book is from Beast's POV, as he comes to love her, the descriptions become for favorable. But she doesn't transform into a swan, no. :)