I agree with the quiet, dark room. I would also suggest you try not to worry to much. Sure, she's not nursing the ideal number of times per day - but she won't starve herself either.
As far as being quick about it, enjoy it! Some babies become very efficient at the breast. Her short sessions does not mean she's not getting enough. It just means she's in a hurry!

Once that next growith spurt hits....she'll be back!
