Hi Dawn-
Oh, that's one of the most difficult things to do.....you're on the right track. Let the others see her, but not be able to touch her during the day. I'd actually do that for about five days. Then, the transition might be a little bit easier. There will probably still be some bickering and pecking though. It's good to make sure the newbie has a place to hide, and also make sure she's getting her share of food and water.
A good friend of mine gave me this advice. He said, when you first put them together, close the door and don't look back for about an hour. They can be pretty mean to eachother, but that's the nature of chickens, and they will establish their pecking order any time a newbie comes into the flock.
A few rules I always follow are, that I never add babies to an adult flock. I wait until the young ones are adult sized before combining them. Also, I try to add more than one at a time, space permitting, so the newbie will have a buddy. (I know you only have one.) Those things just make it easier.
Good luck to you!
Sharon