To me the difference is her face is in her shading. It looks like her younger photo her markings seem to me to be darker and her older photo her markings seem to have lightened at bit.....call me crazy.

With mine I still notice changes in their looks. Abner is 4 years old and he has changed from last year....it's almost like his fur length and overall size is getting larger. Mystic is 5 and has gotten a little longer....and of course a little rounder as well

I personally think all cats are different and the vets can only give us an average of what they have seen, studies, or read.