Just make sure the bag for the girl is a proper womans designed bag, makes such a difference. They are shorter, and sometimes weigh the same.. .. so there is more bag in less area, more comfort and warmth, and the girls tend to need it more than guys.
I prefer Down bags by far.. but the arguement for that is a long unsolved story as synthetic keeps getting better. Some ppl mentioned the North Face bags, they are well built and look good!! Im using Marmot NeverWinter, not the warmest but packs small, ang uses Marmot AngelFire, an amazingly warm bag that also packs small enough....
We could have went into the higher range of down bags, but money was an issue, and these do the job.