I expected Vena's betrayal since ch35 and that she'd use those magical girls against Baiser the second they appeared.
but what did Baiser mean when she said that she cant do "that"?

Maybe because Vena powered up Utena, if Utena takes out Vena then she loses her ability to become Baiser?

I expected Vena's betrayal since ch35 and that she'd use those magical girls against Baiser the second they appeared.
but what did Baiser mean when she said that she cant do "that"?

Go berserk again.

Could be foreshadowing of something we haven't seen yet, considering how much emphasis is put on "that."
If it was something we already know about then she would've probably just called it by name.

what did Baiser mean when she said that she cant do "that"?

Slight confession: I had to take a stab as to who (Baiser or Vena) would be doing "that" as raws just say "それ"をしたら without a specific subject, so I'm a little unclear myself at to what "that" is myself. If a later update shows I messed up, I can get the TS to fix.

@BoobTwinkler, @Goggled Anon
the panel its said on depicts a magical girl's heart, thats used to transform. could it be a hint on Utena becoming a magical girl? though my perception is somewhat scewed, because Ive been playing with this thought for a while (to go along with the expected betrayal. like, Vena takes Utenas powers away and Utena becomes a magical girl to take her out)

Looks like everyone will now get to join forces against Vena. :D

Utena was so close to snapping. All those stars manifesting.

Utena was so close to snapping. All those stars manifesting.

At the same time, look at her eyes: she is incredibly sad, so much that it overpowered her anger.

Theeeeere we go. Actual big stakes now, so it's gonna be fun seeing the girls get serious.
Curious about what Vena's actual goal has been all this time, though. I hope we get some backstory on the magical critters by the end of the manga.

Ah, finally cashing in that narrative check written ages ago. I have to imagine this is gonna be the final arc and I'm very excited for Baiser to properly let loose and demolish the stuffed animal.