Veigar E vs Poppy E

http://vignette1.wikia.nocookie.net/leagueoflegends/images/7/79/Heroic_Charge.png/revision/latest/scale-to-width-down/64?cb=20151124194302 Heroic Charge RANGE: 525 / 300 COST: 70 mana COOLDOWN: 12 / 11 / 10 / 9 / 8

Active: Poppy dashes to the target enemy, dealing them physical damage and carrying them along with her.

• Initial Physical Damage: 50 / 70 / 90 / 110 / 130 (+ 50% bonus AD)
• Total Physical Damage: 100 / 140 / 180 / 220 / 260 (+ 100% bonus AD)

If they collide with terrain, she deals the same physical damage to them again and Stun icon stuns them.

• Stun Duration: 1.6 / 1.7 / 1.8 / 1.9 / 2

Its a targeted dash, which should be stopped by 's Event Horizon.

http://vignette2.wikia.nocookie.net/leagueoflegends/images/8/81/Event_Horizon.png/revision/latest?cb=20130929123427 Event Horizon RANGE: 700 / 375 COST: 80 / 85 / 90 / 95 / 100 mana COOLDOWN: 18 / 17 / 16 / 15 / 14

Active: Veigar forms a cage around the target area which materializes after a 0.5 second delay and lasts for 3 seconds, knocking down and stunning all units who pass through its edges for the first time.

• Stun Duration: 1.5 / 1.75 / 2 / 2.25 / 2.5

Ability Details Event Horizon is a ground targeted area of effect ability.

• Enemy dashes through Event Horizon's walls will stop at them instead.
• Does not apply spell effects.
• Spell shields will block the stun and provide immunity to stuns from the same instance of Event Horizon.

Additional Information:

• Event Horizon deals 1 point of true damage to all units inside the cage and will grant Baleful Strike's passive and an assist if a target champion is killed. In very rare occasions it can even kill a unit when it is at 1 health.
• Event Horizon can only stun a unit once per cast. A unit will not be stunned twice if they walk through the perimeter again after recovering from an initial stun.
• Blink abilities such as Riftwalk and are not inhibited by Event Horizon.
• Forced movement of a unit by knockbacks or pulls such as Rocket Grab through Event Horizon's perimeter will also be stopped.

If she isn't being stopped by Veigar's Event Horizon it should be checked out to see what is going on. Though quite a few RIOTERS have gone on vacation as of recently.

Ali's W is stopped as well