What keeps her young

I asked her
what keeps her young?
She replied
"nothing in particular"
But what is that nothing
I asked her again
She waited a moment
and then said gently
"nothing it's in particular"
When others are getting old
why not she, I muttered
"Let me think over it "she said
and then whispered close to me
"I feel in my twenties
and haven't come out of it"
I got it, I said
what she meant
that's why she remains
in her twenties!