I think if you call the hospital yourself and tell them to drop whatever portion of the medical bills weren't covered by insurance, you have a reasonable chance of getting that to happen.
Beyond that, I don't think you have all that great of a case. There are a lot of unknowns here. The site that you say was used to remove the air is a perfectly valid place to use for truly emergent treatment. Furthermore, as you stated, most of her losses were covered by insurance of some sort. Accordingly, the only thing really left to go after is pain and suffering. And you only get there if you can show (generally) that the treatment didn't meet the standard of care or was negligently performed. I think you have a tough case.
It is entirely reasonable and normal for attorneys to charge retainers in that amount.