Raven can be quite a hard character to pin down a general counter-play strategy for, since she's a highly versatile character with a very open-ended gameplan. But here are some pointers to help with some of the more common tactics you'll encounter.
Countering BT Stance:
As with most stances in the game, paying attention to the frame situation upon entering stance is paramount for both the aggressor and defending player.
If Raven enters BT on negative frames (i.e her BT transition is blocked) then she is more vulnerable to being interrupted or having her attacks stepped. All her BT options will lose to SWL, except for BT b3 (a homing high), BT d4 (generic low that tracks both ways) and BT f2 (her only BT mid to track SSL).
Jabs and some df1's will recover in time to block Raven's BT1+2 if she entered BT on block. Downjab doesn't recover fast enough however, so it will lose to BT1+2 even if Raven is at minus frames. Apart from this, downjab usually interrupts most of Raven's BT options if she enters on negative frames.
Lastly some characters with a generic i12 df4 mid or similar equivalent (Drag, Yoshi etc.) can use it as an anti-BT1+2 option, generic df4 will not only recover in time before the BT1+2 but also creates space and causes the BT1+2 to whiff. Being i12 is also fast to beat out other BT options. Again this only works if Raven is at negative frames.
If Raven enters BT with plus frames (i.e her BT transition hits), then of course Raven is at advantage. Most of her BT options become harder to step successfully, even some of the linear ones (depending on how plus Raven is) and it becomes much riskier to attempt an interrupt.
If Raven enters BT raw (thus the frame advantage is neutral), this becomes harder to predict and layout a counter-strategy formula for and ultimately comes down to your own discretion. Most Raven players are trying to test how jumpy or spooked you are when they do this. Your safest bets are to use movement, either to bait out whiffs or parry attempts.
- Find your characters strongest punish for Raven's qcf4 on block and whiff. Some characters, get a real beefy punish on Raven if they block her qcf4 (especially Anna and Kuni) but what's more important is labbing how best to whiff punish qcf4. Your going to see this move a lot from most online Raven players and it is supposed to be a bait, but it is possible to whiff punish if your positioned at the right place, at the right time (which is what all whiff punishing comes down to). If the case may be you don't feel confident in whiff punishing qcf4, then just backing-off isn't a bad option either. Raven actually loses ground when using qcf4, so hanging back when she does its puts pressure to either commit to an approach herself or finding something else to goad her opponent into approaching.
- Raven's BT snake-edge only launches on Clean Hit, and it suffers the same Clean Hit issue's as Eliza's d3. The Clean Hit range is immensely small and simply holding B is enough to avoid getting launched, even at the wall. Raven's snake-edge, unlike Bryan's, also loses to side-walking.
- Raven's qcf2 / qcf2~1 mixup isn't really a mixup. Firstly qcf2 is seeable (i27) and the mid extension has even more start-up (i40) than the low. It's one of the easiest strings to fuzzy guard or interrupt. Secondly and more importantly, both hits lose to SWL. If you find yourself backed against the wall, don't duck. Its better to take the low if you mentally freeze up. Raven doesn't get much of a combo if she lands qcf2 at the wall but she can score over 80dmg if she lands qcf2~1 which is a wall-bounce (and -12 on block). Of course stepping both is your best option, but if you do freeze up then rather take the low.