Thanks everyone! We live in a suburb and some people think it's ok to let their dogs wander around. Our dog normally keeps guard but we had him inside on this particular day and we were alerted to the attack by our best layer screaming! At first I thought it was a young child that had been hurt! The dog had her by the leg and we chased him off and picked her up. She seemed ok as in no blood or open wounds but would not weight bear. She was being picked on by the other two hens and so we separated them and nursed her back and have finally integrated her back in the coop with them but it has been over a month now. We are new to this whole thing and the hens were given to us so I don't even know how old they are. Could they be too old to lay?
I know this will sound funny but, try sprinkling some crushed red pepper flakes ( free from Pizza Hut ) on floor and let her eat some. Doesn't affect taste of eggs at all. Should start laying within 3 days. If this doesn't work she may be older than you think. Ole timer told me this secret and worked for mine. I had a problem with hen's laying after molt. Try it what do you have to lose but some free pepper flakes.