When an incision opens, they do not necessarily close it again if it has been open for a while. To do so sometimes traps bacteria inside the closed incision, where anerobic infections can multiply and cause a far worse problem.
Often, an opened incision is packed and you are brought back for daily bandage changes, and the dog is put on antibiotics while proper healing takes place.
I echo Jaybay. Get to a good facility, and follow the vets advice. If they don't want to close it, there's a very good reason for that.
Forget the discount. Get her to a REAL vet. Find out where the nearest ER vet clinic is to you and get her there ASAP.
Make certain she is crated during transportation. If crating isn't possible, you'll have to be extremely careful moving her around or her guts could literally fall out. You can use a towel (or any long piece of cloth) as a sling around her midsection. Hold the leash with one hand, and the ends of the towel with another. Hopefully you can have another person come along with you to assist.
For now, your primary concern should be getting proper treatment for your dog. Once she's stable, then you can worry about dealing with the so-called vet who appears to have caused more harm than good.