This is gonna be a wicked turn...

Shelly, let Eevee hit you with the Iron Tail so that you are moved away from her; we don't want to be close to our opponents anymore. Once you've successfully been hit, freeze the downpour of rain around you with Blizzard to mix with the Sandstorm.

The next attacks that are coming are two Shadow Ball's. You are covered in mud, and possibly some snow; odds are, you're very difficult to see, and you're small (hard to hit) anyway... but let's make it even HARDER. Fire the most powerful Confuse Ray you can summon in the diameter of the Sandstorm. We are beyond caring about fatigue now, Shelly, so concentrate hard so that Confuse Ray is powerful and accurate.

Finally, use another chunk of fatigue to summon the largest Rock Tomb around the Blizzard/Sandstorm hell you have created.

We shall go down fighting honorably, Shelly!

Shelly (with very frustrated and evil red eyes): SHELLYYY!!!

Moveset
Blizzard~~Confuse Ray~~Rock Tomb