Jumping away is the best thing you can do. If thrown at the correct height, after you block the pin, you will be in blockstun long enough for Millia to get in for free (which is easy to do). TK pin makes you do extra animation that sends her higher into the air(you can get them on this one, but no one does that). IAD pin is really fast and leads her towards the opponent, so you definitely won't be AAing that. You will rarely see a player throw it at ridiculous height. If they are they are, they're just spamming it and don't intend to come in, they don't know how to use it the right way, they don't plan on coming in, or is just trying to keep you from doing a summon. I think (IIRC) she has the best air to ground advantage in the game, there's a reason for that. What's even more annoying is that she can bait your AA and then you're screwed.
You can try, but as a Dizzy player myself I'm not unless I notice they don't know how to use it correctly after maybe 2 attempts. You should check out japanese vids of Millia players, I honestly can't remember the last time I saw one get AA'd while using the pin.
Here's a good match
http://youtube.com/watch?v=Uscg0MWFuAg
Think of it as a mind game. Do you really want to mess with someone that can stagger you, then knock you down, and play with you for the rest of the match?