I'm all for using MF in sort of a hybrid role(although I'm currently leaning toward AP in my build), but this one seems way too scattered to work. In my opinion, you need to decide whether to go for either Double Up and damage or Make it Rain and AP and your skill order is somewhere in the middle.

I prefer the level scaled runes since she tends to mid so much and by the time she needs to get involved in any serious fights she's usually at level 8+(so you're already getting close or more to the flat runes anyway). Also, why attack speed? Why gold?

Items...Boots of Mobility is a big mistake in my opinion. Take Teleport if you're worried about moving from place to place and go with either Berserker's Greaves(my pick) or Sorcerer's Shoes. Phage --> Frozen Mallet is fine...not so crazy about Tiamat though. For that money you could get a Last Whisper or B.F. Sword and the splash effect isn't worth your time really. You've also got some items that don't really work tremendously well with others. I would say with 9/0/21 and a fairly even skill order, you're going for a skill spam build, so you should either stack tons of damage and crit or stack AP and cooldown/magic pen.

Just my two cents.