i agree with a lot of what lobo said; gotta quit throwing 236B out there so much.
a pattern i started to notice and tried to capitalize on -- after every 4BB, you'd go for 2K. mix that shit up with other stuff (236B, maybe 44B+K, 8A+K, etc)
i often throw out 44K out when i play cassy but it's not the best move, it whiffs a lot and can be stepped on reaction if used too often, but the pushback + oki +44B:A opportunity off of it is great if it connects infront of a wall. if it's a move you decide you like, use it sparingly.
i also fucking love 2B+K. it's fast, tech crouches all highs and many mids, safe, and leads to 4BB:A/crouch throw/oki mix-ups. use it more. also use your B+K more if you anticipate a low or verticle. the sisters' B+K has great evasive properties... it's -14, but people won't often try to punish it for fear of the follow-up B.
i don't think i once saw you complete the 66B+G 4BB:A combo, whether it was intentional or you couldn't get your A to come out. i had problems with getting my jf A out of many combos with strict timing earlier on, and the best advice i have for connecting your combo after 66B+G is to delay your 4BB:A slightly. do your throw, watch them start to fall, and then input the 4B before they hit the ground. it'll make the timing easier to get down.
also, you need to learn the full 33B combo if you're going to try to end it with 4BB:A. (33B A+B 236:B 4BB:A) it's one of her toughest combos but does a ton of dmg if you can get the full thing down. alternately, i'd suggest going for 33B B+K 236B, which still does a good amount of dmg, or 33B A+B 66A+B, which'll combo into 4BB:A if you land it infront of a wall or ledge.
mix up your throws more. 66B+G is great but for the first several games, it was just about the only one you were using. it looked like you became aware of this later on.
last thing i can remember is about throwing your 8K out. 8K has a sneaky sneaky tech crouch at the start and end of its animation but it isn't safe at all; just be wary of that.
all this aside, ggs. i have faith that you can make her the beast she truly is!
quick edit to reinforce this point:
finally, don't make the mistake of doing 4bb:a after every launcher. it is a bad choice. mess around in practice mode. 4bb:a can often be AC'd away. for example, after CH 3b or WR b, don't go straight to 4bb:a. do 236:(B) first, and it will jail them in the air and make 4bb:a guaranteed. being new to cassandra, i would recommend getting into the habit of finishing launchers off with 66a+b at first.
this is completely true and something you should take into account as a beginning cassy. if you truly want 4BB:A to hit, they either need to be grounded, stunned, or have just been launched from 236:B. ANYTHING else can usually be AC'd. you can get stuff like WR B 4BB:A to connect if you time the 4B with the opponent hitting the ground, but it's risky. you're better off with 66A+B or going for your two 236:B.