It's good that she's eating a bit better.
I'm so sorry for you both, that little princess should have this illness.
The sort of treatment I would expect, in this situation is ab's by mouth, & a nebulizer (it's cheaper to buy one) with ab's by nebulizer, drugs to thin the mucus & depending on age, drugs to reduce soft tissue swelling.
Many rabbit vets would start with a minimum of 6 weeks treatment.
You may want to read the thread
http://forums.rabbitrehome.org.uk/showthread.php?t=189817
I'm sorry it's tough reading. Matt was very poorly indeed, & had snuffles treated with repeated courses of Baytril for quite a long time, until a top rabbit vet came to the rescue. It's been a long hard struggle, but we seem to be winning at last.