I believe the brown stripe is cause simply from age. That is one of the ways a vet can approximate an animals age that you have no history on. I agree that if she is eating the hard food (without losing weight) then it is not bothering her to eat it. If she doesn't like canned food, no use giving it to her. I sympathize with the lack of money for vet care, but try to do your best to have her looked at, even if that means calling around for the best price or getting help from a rescue organization that deal with a vet that works for less. Best fo luck and remember, seh depends on YOU for ALL her needs.