Yes, my cat died from that type of infection but keep in mind this was a long time ago before I knew anything about colloidal silver and natural health.
Yes, you can put it her food. One thing though, are you feeding her a raw diet? A raw diet is best for cats (and dogs).
Unfortunately, as far as I know Mesosilver is based in the United States. They may ship overseas but I don't know what the shipping charges would be. Silver made from the Silver Puppy should be fine. The thing is, it's not the same strength as colloidal silver, it is mostly ionic, so for serious infections more is needed. Just make sure that she does not add salt or saline to her silver.
Lastly, yes, you can use ionic or colloidal silver in a nebulizer. Actually, it's very beneficial and I nebulize with it whenever I have respiratory problems.