There are multiple canons, all of which are fluid amongst each other and correct inside themselves.

@Background Pony  
What you’re describing are interpretations that call her a liar, which a lot of bronies subscribe to as well. Mostly, that tweet is misinterpreted in one of two ways: (1) Twilight will die (in the show) before the others, or (2) All of the Mane 6 will become immortal alicorns. (1) is patently ridiculous; (2) is possible, though at this point unlikely, IMHO.
 
The most straightforward interpretation of “Twilight won’t outlive her friends” is that either Twilight isn’t immortal or all of the Mane 6 are or will become immortal. Again, I think the second choice is unlikely, but since an apparent majority of the fandom believes that all alicorns are automatically immortal…

@Background Pony
 
So we are interpreting her phrase “Twilight won’t outlive her friends” wrong as well and she will outlive her friends or will need a normal life until they all pass away, and then she’ll ascend for a second time to become immortal?

@Background Pony  
She said it would have no effect on the storylines of season 4 of MLP:FiM; bronies, as usual, interpreted that to mean more than what she said (“EqG isn’t canon!”) and got butthurt when she said it was indeed canon.

@Background Pony
 
Ehh… Didn’t McCarthy or someone from the show originally say that Equestria Girls wasn’t canon?
 
I’m really beginning to down the authenticity of McCarthy’s words as of late. She says Twilight won’t outlive her friends, but I doubt that. Hasbro may decide it’s time for a new mane6 and have Celestia leave, ascend Twilight for a second time and have her outlive the others.

this is the best bait EVER  
laughed so hard

>Season 5 in a nutshell

@SquiggyBomb  
Why can’t it be both? Spike sets the car on fire first, then he flattens it. No kill like overkill, after all.

But what would be funnier, Flash seeing his car flatened or seeing it on fucking fire?

@Background Pony  
 
 

How could you downvote this? It’s too fucking hilarious.

@SquiggyBomb  
Even better. Spike grows large again a la “Secret of My Excess” and… Well… You know the drill.

I like to imagine Spike set his car on fire for this one.

“Season 4’s Mane Seven”  
LOLNope. EQG may be canon but it has no bearing on FiM so… Good riddance to FS.
 
And Spike >>>>>>>>>>>>> Flash Sentry so don’t ruin moments like these.