Ahh my bad, I didn't see it was her BT low. Although this is a layer 2 read more than anything, so if you can consistently play with it then more power to ya lol.
First off this is Kasumis advanced parry, she only has 3 follow-ups. A throw, an elbow, and the kicks of 4PKK. If you time it correctly, Aya's BT low throw will beat out Kasumi's throw follow-up. For the elbow, miss-timing it isnt a huge deal. I believe the elbow gets crushed by the low throw so you wont get hit. The only thing thats a problem are the kicks, you will get Hi countered if you miss the throw. Anyway ill hop on later tonight to confirm