Goldenrod city gym
talk to her
Whitney uses Clefairy and Miltank in Pokémon Gold/Silver/Crystal/HeartGold/SoulSilver and in the anime she has a Nidorina, a Clefairy and a Miltank.
To obtain TM 45 (Attract), you must defeat Whitney. She gives it to you.
Talk to the person behind the counter in the radio tower and answer the questions. You get a radio card thing for your pokegear and then Whitney leaves.
After you beat Whitney, the Gym Leader in Goldenrod city, you go out of the Gym and into the house to the right of the Gym. There is a woman in there watering her plants and after beating Whitney she will give you the squirtbottle.
Whitney is in Goldenrod City. She has a very strong Miltank so have at least one Pokemon stronger than Level 25
On Pokemon Soul Silver and Pokemon Heart Gold, you have to defeat the Goldenrod City Gym Leader, Whitney, and then she tells you that the construction for the Pokeathlon Dome is complete.
Whitney is in Goldenrod City.
You answer 5 questions in the radio tower in goldenrod city,she'll talk to you and go back into her gym.
In Pokemon Silver, to get the squirt bottle, you must have defeated Whitney. Then, go to the Flower Shop in Goldenrod, which is somewhere in the top right section of the town near Whitney's gym. Talk to one of the ladies inside and she will give you the squirt bottle to spray the dancing tree with.
You can beat her with a Rock Pokemon, or a Fighting Pokemon. A Fighting Pokemon is the best, but if your Rock Pokemon has good moves you can beat her easily. It actually took me a couple of tries, but I beat her with a Quilava, Onix, and a Bird Pokemon (Can't remember the name). Hope this helps!
Its a clefairy