Some suggestions:

1) Smaller enclosure with lots of clutter and cover. Cover 3 sides of the tank with a solid background or paper. This will make her feel more secure and less afraid.
2) Try a live mouse to jump start the feeding response
3) If you're handling her, stop until she eats more consistently.

You don't need to buy her a rack. If you want to simulate a rack for cheap, just buy a small plastic storage tub/tote($3-5) and cover it with a towel. You don't have to use it permanently. Just temporarily until she bulks up and feeds more consistently.