Since Karen's Pokemon are Dark types I'd recommend you use fighting types for Umbreon and psychic types on Gengar and her other's should be Vileplume which you need a fire type to defeat and Houndoom which is defeated with a water type.
He disappears until you beat the Pokemon league again.
beat the 8th gym
the s.s. anne
beat gym leader
beat the league
what do you mean
after you beat whitney.
Earn the national Pokédex, go to the mountain where Red is and beat him.
route 25
Battle the rest of them
after you beat red in Mt.silver
beat elite four rematch