Here is a site off of which you can find out about cat DNA and order a test. The order link is at the bottom. https://www.vgl.ucdavis.edu/services/cat/ancestry/
I know that lots of pet foods made by Purina just aren't good in general, but Killer really loves this stuff, and it was pretty cheap. I've done a little bit of research but all I can seem to find is that it isn't good for older cats because it's rich and it gives them the runs.
Killer is...
she's such a pretty Kitty! I think it's highly likely that she is if not purely RB, a mixed Kitty closely related. The best answers you could get would be from your vet or from a DNA test. You can order pet DNA tests online.