for one thing, what music you like is a stupid thing to fight over- my guy and i have COMPLETELY different tastes in music (me: loud, violent, pounding, him: r&b, whiny british bands), and we've been together like forever.
the main thing- age-gap romances are fun and cool and all- but that is a freaking significant set of years between those two.
you become a completely different person from 14 to 18, and change again from 18- 21, and after 21? your outlook on life has become cemented in adulthood. a 14 year old has no reason to be with a 24 year old, they are in different worlds. besides, it's generally frowned upon and freaking illegal to boot.
besides, if it's for real, it can wait until she is older.