Pogeys Time

Whitney has too many counters now compared to the original.

Trade in anything that makes Miltank useless (Steelix, and Lucario are good examples. I used Lucario with Inner Focus and Aura Sphere. [Making it female seals her fate])
Kill a crapload of trainers for money and buy one of those high damaging TMs and destroy her
Heracross Brick Break, dead (Has to be faster and preferably female)
Use X-items..
Trade Drowzee for Machop (Make sure Drowzee is female)

The easiest and shortest way is the last option. I went with the first option because I already had a Lucario ready to be traded in, along with a Piplup, and Chimchar.

I'm actually glad they gave the X-items some more use, there wasn't really a point in earlier games to buy those. Just parlyze it then destroy it with a heavy hitter, and as you can go all the way up to Sudowoodo before fighting the gym you can get quite a few extra levels.