If Thanos snapped in Equestria

[FlareGun45 2,221]

So let's say the events of Avengers: Infinity War affects Equestria as well - who would you say got affected by the snap?

[cuteycindyhoney 13,308]

Why would they not? Equestria is in the universe. That snap reached all of creation!

Pinkie

Maude

Rarity

Derpy

Big Mac

Scoot-a-loo

Mayor Mare

Shining Armor

and Luna all turned to dust.

 

[Megas 27,737]

The way I look at is who I cast as in the movies
AJ
Dash
Twilight
Rarity
Fluttershy
Spike
Pinkie
Mane 6 + Spike are safe

Sunset Shimmer is fine

As for the supporting cast

Big Macintosh
Coloratura
Starlight
Cadance
Pie Family
Zecora
Scootaloo and the rest of the CMC, and probably most of the notable classmates save for Pipsqueak
Scootaloo's aunts
Gallus
Yona
Sandbar
Ocellus
 

All get dusted

Spitfire and the notable Wonderbolts(Soarin and Fleetfoot) are fine
Cake Twins are fine
Smolder is fine
Tempest is fine

For the ones not going by the casting, anyone I didn't mention is a coin-toss

It's up to you to find out who's who lol

This was really grim to think about

[Quantum Pony 40]

The infinity gauntlet only has power in the universe it is created. For Avengers: Infinity war this would be the universe designated as Earth-199999. Since Equestria  is likely in a different universe (or multiverse), they won't be affected at all. 

Let us assume they are in the same universe. The infinity gauntlet has its own limits and I doubt is has any power over a realm protected by a creature of incalculable power: Pinkie Pie.