So sorry you are still having problems...
4 regurges are A LOT. I normally would be really guarded about the prognosis after that many, but the fact that she is still healthy, strong, and in good weight gives hope yet for a recovery. Also, the fact that she did very well until the feeding of 2 pinks is a good sign too.
Since you already have tried just pinkie heads without success, I would go to a few liquid feedings via syringe, along with Nutri Bac. I would use cooked egg yolk (no sense in adding more Salmonella than she already has!), meat baby food, or a cat food pate', or some mixture of those. Strain them through a tea strainer to make sure they will go through the tube, adding a little water to make it go through a little easier. If she is hatchling sized, I would give 1 cc of the mixture (with a pinch of NB mixed in). More if she is bigger. Sit down and put her tail between your knees, holding her upright in a vertical position, and keep her vertical for a minute or two after the feed so it doesn't come back up. Have a friend help if you need it. Repeat every 4 days or so. The liquid should be very easy to digest. If she can't digest even that, then she has some serious problems and the vet may need to do some cultures. If she digests it ok, then keep it up for at least 2 or 3 weeks (with a good pinch of NB each time) before trying another pinkie head. That should give her some strength and maybe get her digestive tract back in balance a little.
If you can't find a feeding tube online, maybe the vet can help. If you are nervous about tube feeding, maybe the vet can demonstrate, if he feels it is a good idea. As long as you avoid the opening in the bottom of the mouth (where the snake breathes), and keep it vertical for a minute or two, it should be pretty safe. What you are doing isn't working, so unless the vet has a different treatment, you are likely to lose the snake if you continue on the same treatment plan.
BTW, I have never found bloodreds to be particularly susceptible to regurges, although each family line may be different.
Hope it helps - let us know what happens. Good luck!