Do you know, they do make me mad sometimes. Why do they insist on giving you the worst case scenario with nothing to back it up.
They know she has the little hole in her palate which leaves her open to infection, so in Kali's case THAT is the most likely diagnosis and THAT is the first thing your vet should be thinking of. Why on earth would she make her first thought a tumour in that situation?
All she has done is make you more worried and I honestly think that part of any health carer's job is to reassure where possible.
Anyway, off my soap box. I really hope she improves with her antibiotics. Although again, I would think that any infection in there could be quite deep-seated and may need a much longer course.
In the meantime, try not to worry too much.