Rate My Friend's Party....... Venusaur LV 35 Solarbeam Razor leaf..

Train them equally and get a diverse party.

I would rate it a 6/10.

Your Venusaur can't kill any poison, fire, flying, bug, or steel types.
Replace some of it's moves.

I think he's got a good (not great) party, but I do have one suggestion, replace Butterfree's Gust with a stronger aerial attack.

I need to know where your friend is in the game, but I'm assuming that your friend is at Fuchsia City if she's gotten a Vaporeon. Finally, someone with an Eevee evolution in their team! Great choice.
Venusaur: Why all grass attacks? Try.. Hmm... Grass Pokemon are WEAK against a lot of types. Give it Sleep Powder and Toxic because you can put your opponent to sleep or poison while you think out an alternative method. Keep Solarbeam and teach it Sunny Day- this moveset is meant for stalling for time, and hope your opponent's Sp. Def stats are weak. If you are planning to use Venusaur in the final team against Elite Four, you'll need a really good moveset.
Butterfree: Not a good Pokemon I'd choose. If you caught a Pikachu, it's a better Pokemon than Butterfree, and once it's learnt Light Screen, Evolve into Raichu with Thunderstone.
Vaporeon: Keep Water Pulse if you like, or replace with Surf. Replace Sand-attack for Ice/Aurora Beam, and Quick Attack with Toxic/Haze. Vaporeon has impressive Sp. Atk stats, should be good for attacking your Rival's Charizard at the Elite Four.
Snorlax: If it has Immunity as it's ability, use it un the final team against the Elite Four (particularly the Ghost/Poison user Agatha). Replace Strength for Body Slam and Headbutt for another move (as long as it's nor Normal-type move).
Pidgeot: Too many Flying moves. Replace Fly with Sand-Attack. It's not a Pokemon I would recommend for the final team against the Elite Four.
Diglett: WHAT?! Not dugtrio? Replace with Onix if you have it. Moves are good, but replace Cut with anything you like. Watch out for Ground/Rock types if you're keeping Dig, Earthquake/Magnitude does double damage while you're in the ground.
Of course, I'm assuming that this is a temporary team that will be replaced with better Pokemon soon. Put an Electric-type on your team or Lorelei(Elite Four No. 1) will be hard.
Prof. Eevee

I would give it a 5/10.
Level them up more.