baby chick badly hen pecked, what to do?

Hi,
We just had an incident today where one of our baby chicks (1 1/2 mo old)got
herself badly hen pecked today by one of our older pullets. I found her this
afternoon huddled in a corner her head all bloody and no feathers left. We
brought her in the house and put her in the box we had left over from when
they were day old chicks. She is very lethargic and is not interested in
eating or drinking. We are trying to keep her warm with a heating pad and
blanket (our one heating lamp is in the chicken coop with all the other
chicks). Is there any more we can do other than just wait it out? And what
can we do to keep this from happening again. When we first introduced the
new chicks into the coop we kept them in a separted cage built out of
chicken wire so the older chickens could get used to them. When they were
all too big for that we let them out and now they are all outside during the
day free range. I've been watching the older chickens during the day and
only times they seem aggresive to the chicks is when they enter the coop to
lay eggs. I've seen them corner one of the bigger chicks before but never
hurt them because I stopped them before it could. Any suggestions? Since
they are free range we cant clipp their beaks, right? Thanks for any info.