Sabrina uses Psychic Pokémon. They're pretty easy to beat if you have...any bug Pokémon! *grins* Parasect is very good in this gym, since they learn Spore at L30 and with Leech Life built in, you can take down any of Sabrina's Pokémon easily since Bug has an advantage over Psychic. ^_^

Sabrina's gym is very confusing, because there's teleporters in each room and they take you to different rooms so it might take a long time to get to Sabrina. But here's an alternate way :

Everytime you get to a teleporter, always go to the one above or below you, then count the floors. Count to 15, and if you see a girl, that's Sabrina. ^___^

Her Pokémon pose no threat if you have any strong Pokémon at the top of your bench(mine was Charizard). But if you have a POISON Pokémon at the top of your bench, you might have a little problem since Psychic has an advantage over Poison. -_-; So that means if Beedrill were to fight(if, it has learn Pin Missile/Twin Needle), Beedrill could lose, because Beedrill is part poison.

Gastly and Haunter aren't good choices too, since they're part poison.

On the other hand, since Psychics have AWFULLY HIGH SPECIALS(check out Mewtwo's - 300-over!), you might want to try non-special attacks. =)

If you win, you'll get the Marsh Badge, which will allow Pokémon up to L70 obey. =)