Maybe because there’s too big of a range and I don’t think she could dedicate her full concentration to teleport 4 other ponies if she is falling and stuff. On a slightly unrelated note, when people start saying “Why didn’t she teleport at that moment?” whenever she’s in danger is getting a bit annoying. Have none of you considered the fact that she might have to actually SEE the place she teleports to? But who the hell cares anyway, it’s a cartoon

Dragon Quest: It takes Twilight two tries to teleport herself, 2 other ponies and a dragon in a tense situation.

Because she can’t concentrate enough to do it in near death situations

Yeah, because as we all know, Twilight thinks well under pressure. (Hint: That’s sarcasm.)

Because Twilight Sparkle sucks when it comes to acting fast.  
It’s a Rainbow Dash’ thing.

Considering this is a Merriwether Williams episode, I’d say shoddy writing.

I’m sure it takes more time and concentration to teleport a group of ponies, not to mention the situation was so sudden. She would have had to think pretty quickly to do that.

@elementofchaos7
 
This. They all probably expected to do some cloud-walking.

As mentioned before, conservation of momentum.
 
Also, teleporting probably requires concentration, something that Twilight apparently doesn’t have when plummeting to her death, as seen time and time again.

Teleporting more people is harder. I meant to say that.

@Gomenasai  
Twilight probably cast the cloudwalking spell already.

Teleporting more ponies, especially while in motion, is teleporting just herself. Her teleports might also preserve momentum, in which case it wouldn’t have helped after they started falling.
 
She also has difficulty focusing enough to do so when surprised. Given that she singed Spike the only time that she accidentally teleported, it’s probably for the best that she didn’t.

because the teleportation puts you in a new place but it doesn’t stop motion. at the speed and velocity they were going, teleporting would still have had them hit the ground fatally.

^ Dash made the cloud really dense?

More importantly, why were they able to bounce off of the cloud RD prepared for them when only pegasi can touch the clouds?
 
Plot holes, plot holes everywhere.

WTF, man? Is this an unmarked spoiler?  
TAG YOUR UPLOADS!

Doesn’t the teleportation spell only take you to places you could walk to?

Twilight is awful about quick thinking in critical situations for one :T  
second I’m not sure she can accurately change her altitude during teleportation

Doesn’t the teleportation spell require focus of the user?

because this was a RD episode.