My sister's party is OK. But I thought you guys would do a better job at..

She's chosen some bad pok�mon, and why two Vileplume's? Anyway:

Blastoise: Oh no, why didn't she start off with Charmander or Bulbasaur instead? If she wants a Water pok�mon tell her to get a Lapras or Starmie, they're better than this poor guy. Anyway, if she wants to keep it, give it:
Surf
Rest
Ice Beam
Earthquake
And remember that Hydro Cannon, Blast Burn and Frenzy Plant are all bad moves and should never be used.

Vileplume: Vileplume has one good moveset (and it is good, actually. Vileplume isn't a bad pok�mon, but Victreebel is better):
Sludge Bomb
Solarbeam
Sunny Day
Sleep Powder

Vileplume: Drop for a Fire pok�mon, Arcanine strongly recommended, or maybe Ninetales.

Kadabra: Where is Calm Mind? It needs Calm Mind. Keep Psychic. Its moveset should be:
Calm Mind
Psychic
Ice Punch
Fire Punch

Hitmonchan: Umm, get rid of the elemental punch, Hitmonchan has bad Special Attack, and isn't a great pok�mon. Best moveset:
Counter
Sky Uppercut
Brick Break
Substitute (if he learns it)

Wigglytuff: Words of wisdom: Wigglytuff sucks so get rid of it. Ugh, if she considers keeping it:
Seismic Toss
Thunder Wave
Sing
Rollout
She needs to lose this thing, for something Electric like Magneton or Raichu.

Not very good pok�mon choices. But surprisingly she got the Wigglytuff moveset pretty good exept for Mega Punch.