As a female POW, PFC Lynch probably had more propaganda value to the Iraqis alive than dead...
...at least up to that point. They hadn't had the opportunity to make use of her in that way yet. Possibly the reason for the broken limbs was her, um, reluctance to participate in issuing a press release.
If all the men were killed, I'd bet that's why she was still alive. The novelty aspect of a girl soldier may have been a factor too.
Regards--
Mary Anne