Always block low vs mileena. you can see u+4 coming for days, it's easy to block on reaction, but d+4, or even b+3- which leads into full roll combo's, are a little harder to see.
After the u+4, she has advantage, but not enough where she can throw another u+4 without it getting interrupted, so if you see her trying to double up on u+4, punish her. however, she can do a u+4 and can do a 4,2 and this a true frame trap and it can also lead into full combo's, so be careful if she tries to change it up.