Some tips to keep in mind.
-You can start teleporting as Anivia before you die, and continue teleporting while Eggnivia (so long as you aren't Hard CC'd). Super situational, and many would argue Ignite is better on her anyways.
-Casting your wall at the perfect moment will interrupt pretty much every dash that isn't unstoppable. For some reason the way gap closers work, if terrain is made in their path during their jump, even if they can clear it, it will displace them. So if you can get the timing right, you effectively have anti-mobility.
-Don't be afraid to drop some damage for tankiness if you're dealing with assassins everywhere. Due to the amount of mana and mana regen you buy, sacrificing some burst for survivability will give you more time in fights to hang around while remaining relevant because her base damage is obscene. Plus it's just hilarious when you get warmogs and everyone has to stop for an hour to kill Eggnivia in the middle of a team fight.
-FREAKING GET MS QUINTS WHY IS A BIRD SO FREAKING SLOW