For our company, Belle is doing a more "posh" accent than her normal australian one. The director calls it an international theatre accent. I'm not sure if that means anything to anyone else or he's just making it up.

Babette and Lumiere are both doing strong french accents in their lines and their songs.

Cogsworth and Mrs. Potts are both doing kind of... mild cockney accents.

And Madame (Me!!) is doing the same as Belle.

I don't think it really matters what accent she has really, as long as it's understandable and convincing. I could be way off base though

I think you should just be natural, focusing on the accent might have negative effects on your performance as an overall, so be careful.

I'd go for a wispy kind of American. The American accent has a tendency to be really rough and sharp, so if you put a dreamy, almost French fluidity to it, you'd be golden. She's really up in the clouds when she's in the town, but the dreaminess would dwindle in the castle, excluding the scenes where she's lovey with the beast.

The performance I saw at a local Dinner theater the Girl playing Belle had an English accent.