Going to revise what I previously wrote above and try to dust off some cobwebs on this thread for this writeup. Recounting the sessions I did against Faultydefense and previous experience mentioned above I'll try to explain things the best I can.
This matchup is a momentum based matchup as to whoever gets the first knockdown wins and neither character has an answer to get out other than blocking correctly. Fortunately enough Millia has the advantage in terms of mobility and pin to help her secure the knockdown and okizeme.
-Pin shuts down venom's anti-airs and stops venom from setting up balls. Fish for pin counterhits for knockdown.
-If you do not have the pin, be wary of your movement as Venom's anti-airs can be converted into his pressure and corner game. In addition, watch for pool balls since they will likely be set up already.
-Maneuvering around in the air and utilizing your mobility is highly suggested. Take the initiative, but don't get reckless against his anti-airs. Turbofall is good to mix in aside from your airdashes.
-Venom's DAA is baitable when canceling strings into roll at times.
-Avoid rolling in neutral situations because of 2d and 6h.
-j.k is good when he is above you as mentioned.
-Venom's 5sf and 5h are strong pokes that can lead into knockdown along with stinger frc. 5p is also quick. Do not go poke for poke against him.
-His pressure can crank your guard bar quick and they leave him. Do your best to block correctly and don't mash out.
-When you don't have the pin, Venom does have a higher rate to anti-air you and can set up balls.
-6h reaches all the way to the ground so using roll in neutral is not advised at all.
Will edit this post definitely to add or correct things.