I read the bit linked to and didn't get that impresssion, jane. Just read some more. I think she is seventy-five. I didn't comment earlier because I found it rather a tedious read. It's sooo "the thing to say". Yuck.
To be perfectly honest, I'm tired of hearing that sort of phrase: "n in my head but in an n-aged body" where the second n is a larger integer than the first. If I still felt, say, thirty in my fifty-eight year old body, I'd be ashamed of myself. You can learn a lot and experience a lot and develop a lot (wisdom even!) in twenty-eight (or however many) years. Dismissing that as somehow not really you because you still feel the same as you did n years ago (where n is a large postive integer) is tosh and silly in my view.
There is nothing wrong with Growing Up. It doesn't have to make one a predictable bore saying whatever is fashionable and 'cool'.