Advice needed with chicks-one younger than the rest and is getting picked on

I got 7 chicks on 4/4/16 from Southern States. They have been so fun! Now 6 of them are fully feathered, as they were a week or two old when I got them (left over from the previous week's delivery). The last one is a Golden Laced Wyandotte and she is only now getting feathers other than her wings. Currently they are in my garage under a raised heat lamp.

The 6 older birds are ready for the coop. But the GLW is not fully feathered so she isnt. I dont want to separate her from the flock but I noticed this morning that the bigger birds are feather pecking her. Her bum has a small patch with the fluff removed. I dont want her to get hurt, but I'm not sure what to do. I know it is because they are too big for that space now.

Any suggestions? I've thought of a few things but I am not sure what is best. 1. Separate out 5 and leave her and friend in there until she can go outside. 2. Keep her alone 3. Try to convince someone to sell me two ducklings and stick the 6 outside (id love to have a pair of ducks but I am not sure I can find someone to sell me just 2). 4. Put all of them in the coop and hope she makes it.

Putting the heat lamp in the coop isn't an option as we don't have an electric source out there. I am quite worried about her and want to stop this before it gets bad.