What it seems like they did was make B3's current hitbox more consistent, so the actual hitbox isn't changed it just hits where and when its suppose to. In the process (idk if it's actually a stealth nerf or not) they made it so after Mileena lands a raw roll and goes into B3 that the float state of the opponent is decreased.
So after Roll xx B3 the opponent is lower to the ground and falls faster(so basically less hitstun, more hitstun deterioration), but Tele-kick's hitstun naturally lifts the opponent higher into the air so Mileena can do an air sai for an extended combo. The problem with this is because of B3's decreased hitstun you have to IMMEDIATELY input Tele-kick, otherwise the air sai will whiff. Also I don't know if Mileena could before but with Roll xx B3 xx Tele-kick xx Air Sai xx B2,1,2+4 she can't make the B2. So if she could before she lost the extra damage from that string.
Honestly all the more reason for air sai to have less recovery and for tele-kick to be faster. She shouldn't have to trade off for a 15f AA that leads to 35% or one of her most damaging combos off roll. Maybe im just salt but I don't really like the change. I think this was their way of balancing Mileena out. Faster normals for basically decreased damage off roll.