OKKKKK! I assume you know most of Scorpions weaknesses.
Mileena relies heavily on her Mix-ups and her offensive is OK, but not the best. She only has one low starter with a ton of overheads.
All I'm saying is block high and when you get that feeling that she's going to hit low block low, Most of her damage comes from punishing combos so be careful with your teleports and spear, Never.. NEVER... NEVER resort to hell fire against Mileena. Idc if she's throwing sais from fullscreen cause she's trying to either bait the teleport or Hellfire.
Now for your offensive options.
You want to get her into your vortex mix-up, How do I get her to commit to it you may ask.
Simple, No matter what version of her teleport she uses she's still unsafe. After a blocked teleport, D+1 into spear and go straight into the vortex mix up.
Pressure strings, 1,1,1 is one of scorpions fastest and safest strings in his arsenal and can lead into some options into vortex.
Example. 1,1 Dash cancel into grab you getting roughly around 13% damage if they take the chip and not tech the throw, but ever little damage counts
Another would be 1,1 into F+3(low hit) but this is risky because Scorpion has to hit confirm into spear to start up his vortex off this pressure string and if they guess right you can take some serious damage.
EX teleport vs Normal teleport (Scorpion)
Normal teleport on block is risky and is only situational, but EX is safe on block and can lead into the 50/50 vortex
After a blocked EX teleport you can either B+2, F+3 or either 1,1 into grab or 1,1 Dash cancel F+3
I don't mind helping people up their game, good luck
But OP you should ALWAYS block low against mileena as they are instant hits. You can react if you're quick enough to block high on all her overheads minus her EX ball roll. Meaning her U+4 you can block on reaction. If you watch for her feet leaving the ground, you block high.
But it's a lot harder to do on reaction online, so you "might" a little bit want to try just predicting/reading the mix ups. But If possible I suggest blocking low, and blocking high on reaction to UP+4
Also when it comes to Scorpions mix ups on his Vortex.
I generally only agree to Vortex now if the following conditions are met
1.) Your opponent is better than you.
2.) You're behind
3.) You're slightly ahead both you and your opponent over 50% with a breaker.
IF you're better than your opponent at reading, why would you play a righ risk high reward game with someone worse than you?
2.) IF you're behind vortex is a great comeback tool because it's essentially a coin flip for every roughly 20%-30% damage. Playing standard opens you up to chip. but if you guess right 50/50 chance. You get another round of free damage w/o taking any damage / avoiding pressure.
3.) IF you got a breaker and you're barely ahead. You can take a chance and try to see if you can seal a bigger lead if you want.