Is it possible you're feeling old yourself? You saw someone you thought was much older & it turns out she was essentially your age.

Now you take me, for example. I really am old! I sometimes see other people my age & I think: "OMG, am I really THAT OLD?" I tend to look a bit young for my age, I think. So when I see someone who is my age, & they're faces are wrinkled, & they have gray hair, & their overweight, it really drives home for me how old I actually am! Maybe something similar is happening with you.