Just want to add (for others too that may come across this thread):
A homemade incubator can be made out of a small or medium sized dog kennel, the plastic kind, by placing a heating pad, set on 'low' under only half the kennel (not inside the kennel). This allows the pup to move to a cooler area if she gets too warm. Young pups normally have the extra warmth provided by being with their littermates, and warmth helps with the digestive process.
Also when feeding with syringes, I use four 3cc syringes, fill them with what ever and fit them with the rubber nipples. Then I put them in a mug filled with hot water (checked with a meat thermometer). As I am feeding, if the syringe cools down before the pup finishes, I put that syringe back into the hot water and start with another one. This way, I always have a supply of warm food throughout the feeding. (I always test a drop on my wrist before offering it to a pup).
Another thing to try is how she is positioned while feeding. Some pups like to be more on their back, some like to be more forward. Some like more contact, some less.
And definitely put Carmen's number on your speed dial!