For me, this is the match that lag helps Raiden the most out in. In a clear connection, my Mileena has little trouble with him. But in any lag, Raiden is much more difficult. When you 15 streak someone in a fast connection, and then only win 3 out of 4 in lag, obviously there is a handicap going on with lag. Still, Raiden's unpredictability and versatility make him harder for Mileena than most fighters.
RAIDEN
Superman from all different heights to catch Mileena when she's sai tossing. Go nuts with the teleport- you have to keep Mileena confused if you are to win this match. Even though Mileena has the better jab, with the teleport, you can surprise her and then jab before she can. This forces her to play defensive. Lightning bolt is only useful as a projectile trade. Shock grab is very important here, but don't overuse it, or you open yourself up to big damage. Do NOT let Mileena run to a corner. She is in complete control of the match if she is there.
MILEENA
Ground sai toss instead of air sai- you're too vulnerable to supermans in the air. Raiden usually supermans from ground level, and the ground sai will stop him. Block all supermans and immediately drop kick. Anticipate his teleport by buffering the roll so that you hit him as he morphs next to you. Jab is a great idea if you can get near Raiden on your terms. Her jab pressure beats Raiden and her sweep will not only outsweep him, but also hit him out of supermans if he's in the start-up animation. Sometimes this match is easier to win WITHOUT using sai. If you're getting killed, run to a corner. This sets up your 70+% combos. It also takes away all options for Raiden to hurt you. This is a douchey play, but it's why she owns Raiden. I only use it for tournaments or ranked matches.
I'll say it's a 7-3 for Mileena, because Raiden definitely has the moves to always keep her on edge. But when it comes down to it, she will probably win anyway.