For the moment i would be more concerned with how much weight you say shes lost. 4 weeks of not feeding is not enough time for her weight to drop so much that you can see her spine. i definetley advise book an appointment with the vet and get him to do a check for parasites.
As for feeding issues, take a read of those previous threads Malc posted.
Reptiles & Amphibians
0.1.0 Corn snakes- Sniv.
0.0.1 Jungle carpet python - Vinnie,
0.0.1 cali king snake- Cali
1.0.0 Hognose - Pinnochio
0.1.0 Royal Python - Daenarys
0.1.0 Sand Boa - Dune
1.0.0 Green Bush Ratsnake - Forest
0.1.1 Amazon Tree Boa - Igni & Onyx
0.1.0 Leopard Gecko - Nyx
0.2.0 Siamese cats - Nala and Duchess,