Blocked Valerie BBC Interaction Explained:
Valerie should BBC a lot in this matchup. Rook is okay to let her, but needs to be aware of what she will try to do afterwards in order to survive her offense. There are some amazing interactions happening here, but the first layer is whether the BBC actually happens at all.
If Rook has S, it's VERY HARD to BBC him. He can fire off his S right after the 2nd B in the chain, guaranteeing the S hitting Valerie and dealing 3 damage.
Valerie can BBbB to not die to Rook S in between the Magenta-Yellow part of Three Colors. If she spaces it wrong, the vines will still get her, so she has to do a lot of bBbB (if too far it won't hit) into bB. So spacing is crucial. If she's greedy and knows he'll go for it, she can actually do fBfBC and she'll sail right over his super and punish him with another BBC if he's not carefuly.
As Valerie, If you think Rook will NOT super (or he doesn't have it), after any BB you can do either bB (safe) or C (risky, but sets up the following interaction).
Here's where most of the fight takes place:
After Rook blocks Valerie C, Valerie is -2 and sets up one of the most interesting mixups in the game. If Rook presses f. A after blocking Valerie C, he will ALWAYS Throw her. I'm serious, try it against literally anything that isn't Super, including raw Jump. It's fast enough to beat all of her moves, and catches her pre-jump frames without any advanced sort of buffering.
However, this is a Throw that Valerie can Yomi Counter. She gets very high reward off of doing this, as the hard KD and guaranteed chip setup deal 1-2 damage. So your first instinct as Rook is to command grab her so she can't YC the normal throw, but you'd actually be wrong.
A lot of the time, the Valerie player will wait a split second right after the blocked C to see if Rook went for the "automatic guaranteed Throw for 2 damage". If he did, she will get the YC, the free damage, the free disc, and the oki setup that chains back into BBC and starts the ride all over again.
If Rook doesn't go for the fast Throw, she can try to delay her jump to beat a variety of things, but will lose to a couple of key Rook options. She could also do a n. A attack, which is risky but you'll see where it lands in the mixup in just a bit.
So now Rook is on the defensive; here's what he can do after he blocks Valerie C, in terms of the "best thing" to the "worst thing".
-Throw. As explained, this wins 100% against everything that isn't Yomi Counter or Super. You must represent this at least a little bit to activate the rest of the mixup, because the damage and oki you get off of it are too amazing to just let Valerie do what she wants each "turn".
-n. A. Hits a "not-blocking Valerie" and gets a hard KD, setting up his oki game again. If it's blocked, that's okay, he's +3 and can mixup either f. A (early timing) or a normal Throw (late timing). If Val blocks that, she's now flashing with chip. Valerie CAN hold j to not get hit by the sweep, but she is afraid of normal Throw so it's dangerous for her to try this. The other thing she can try is n. A specifically to beat your n. A (you aren't trying to YC anything so you will always block it). The scary thing for you is that it will actually Counter Hit your n. A, so she'll get 2 free damage by comboing it into Yellow. Your n. A also loses to Valerie S (which she can use to beat fast Throw), but oh well, she doesn't have her disc anymore and you took 1/8th damage. Go you!
-Block. She might just do delay jump, B, which you can blow up hard with delayed C or delayed Super, so just Blocking is a pretty good move here. However, if she reads that you'll never do anything, she might just BBC again for a guaranteed damage and the process restarts, but it's very risky for her to attempt another Cyan right away after being -2 against a guy with armored moves, so chances are she won't.
-Delayed Throw. If Val wants to delay her jump for a split second, and then jump after, delay your Throw to catch her prejump frames. The timing on this is very tough but the reward is high, though if you're wrong you're probably going to eat a j. B, BBC (because you got a big f/b. A instead of Throw) and restart the chain with a lot less life than before.
-C. The weakest option. If Val wants to "just Jump" to beat n. A, she also beats this, and if she wants to "delay Jump" to beat Throw, then she's also beating this, and it doesn't actually take any sort of presence of mind to NOT get grabbed by Rook C. The only thing you are beating with this is if she mashes S (which you would just press something after the flash, maybe even your own super instead for 3) or the awkward greedy n. A that Valerie might try specifically to beat only n. A. Valerie could also beat this with b. A, but she'd probably just rather do j. B, BBC again. Note: There is a crazy tight spacing where she can get away with n. A into bB, but she doesn't get to OS against n. A and C reliably. So C is still very much a part of the mixup if you are using a lot of n. A in the situation, but keep in mind it just gets blown up very easily if you're wrong, so it's a hard read on a single option which isn't great value overall.
-S. Actually the real weakest option, because it's really not an option. Just like with C, 99% of the time Valerie is going to do early jump or delayed jump to beat all of your options, and if you mash S after she lands she can literally hold J and blow you up. She can sometimes get between 4-5 damage depending on how close she was to you when you did it. Again, sometimes she might n. A, but it's very low on her priority list of what she should do. Typically, you are trying to use this in between the Magenta and the Rainbow Stroke (between B and C) so that the mixup doesn't happen and Valerie has to do a lot of BBbB instead of BBC. However, sometimes Val can be disrespectful and go for a BBC when she's CLOSE enough to you, and it will sail over the S, giving her a new BBC punish after the fact (and now you have no meter! Sad for you).
So here's the decision tree, actually.
After BBC, Valerie might:
-Delayed Jump. Beats Normal Throw, C, S. Rook should n. A, Delayed Throw, Block (Delayed C, Delayed S based on situation).
-Instantly Jump. Beats n. A, C, S. Rook should Normal Throw, Block (Delayed C, Delayed S based on situation).
-Block/Walk Backwards. Beats n. A (but not really), C, S. Rook should Normal Throw, Block.
-n. A. Beats n. A. Rook should Normal Throw, C, S, Block.
-S. Beats Normal Throw, n. A. Rook should C, S, Block.
So as you can see, "just blocking" is actually a great idea against all three, but then you're just letting Valerie get away again, or do what she wants if she can bait your delayed C (or if you don't have S to guarantee safety against her j. B). Normal Throw is the "best" option, but us Yomi players know what it means when there is a clear best option . n. A is very safe and only loses to Valerie's greediest option, the n. A/S.
Alright, that's enough Valerie vs. Rook jargon for now. There's a lot more to this matchup, but this is the part where a player who has studied the mixup might just run all over the other player who doesn't (on either side!), making the matchup seem really bad for the non-knower.