I did some digging over at the Compendium. Although the question was not answered directly under "Flower Dance," I think I did find something that applies.
"Q. Will a Poliwhirl attached to a Brock's Nintales count towards Politoed's Frog Song?
A. Yes it will. (Aug 9, 2001 WotC Chat, Q260)"
Neo Discovery Politoed's Power Frog Song:
"Whenever Politoed’s attack damages the Defending Pokémon (after applying Weakness and Resistance), if there are more than 3 Poliwags, Poliwhirls, Poliwraths, and/or Politoeds in play (including your opponent’s), that attack does 40 more damage (no matter how many heads you get). This power stops working while Politoed is Asleep, Confused, or Paralyzed."
Since having a Poliwhirl on Brock's Ninetails counts for Frog Song, I do not see any reason why a Bellossom on Brock's Ninetails would not count for Flower Dance.
I agree with PokePop, though, that multiple Bellossoms on the same Brock's Ninetails would not have the effect you are hoping for.
I hope this helps.