In "Her First Ball," what is the fat man saying about losing innocence and what is Leila's reaction to this?

Beneath his point that time is a thief who robs young
ladies of their naivete and youthful joie de vivre, the older fat
man pronounces much more about himself than he does the concept of the brevity of
youthful delight and innocence. His words to Leila are, indeed, telling of his cynicism
and loss of youthful idealism that is like "little satin shoes that chased each other
like birds."

It is because he himself is a
disappointed romantic who has lost his own youth and its accompanying delights that he
seeks to destroy Leila's innocent and youthful delight in her first ball.  For, Leila
becomes the target of his cynicism in order that he can steal from her the enjoyment of
the moment.  This is why he is yet on the dance floor at his age.  Indeed, he speaks of
himself and his personal losses, rather than the ingenue he holds when he presses
himself to her as though to draw youth into his own
being:

"And
your heart will ache, ache"...because no one wants to kiss you
now."

It is Leila's intuitive
comprehension of the fat man's motives--"Why had he spoiled it all?"--that she rejects
his cynical statements that youth and beauty are but temporal.  This is why she rebuffs
his condescending remark, "...you must'nt take me seriously, little lady" by saying, "As
if I should!"  Rather than becoming disillusioned and cynical herself, Leila chooses to
enjoy the moment and delight in it for what it simply is.  She "didn't even recognize
him again."