I'm rewatching season 2 of the anime after catching up with the latest chapter of the LN.

Satella appears in the Sanctuary, kills Emilia, Ram, Otto, and everyone else besides Subaru. She also tris to kill Garfield, but Ram saved him. She starts heading away from Subaru. The assumption Subaru makes is that she's headed towards the mansion to kill Rem, and likely Petra and Frederica too. This is most likely accurate.

So, what specifically provoked her to kill all the people Subaru loves?

Was she enraged specifically by Subaru revealing RBD to Echidna? Was she privy to what was taking place at the tea party? I assumed she couldn't follow his soul in the tea party. That's why she couldn't prevent him from telling Echidna about RBD by killing him and/or Echidna.

All I can think of is that Satella was still able to OBSERVE what was going on at the tea party and became envious of Echidna and enraged that he shared "their secret" with another woman, and even worse, another witch. Unable to exact revenge on Echidna herself, she starts killing all the people Subaru loves in a blind rage.

Echidna, knowing this was going to happens, chose not to warn Subaru it was going to happen (not sure why, just seems like there was no reason not to warn him, but also no reason for her to warn him either), but she enchanted the handkerchief so that it could be turned into a blade that Subaru could kill himself with.

Any holes in this theory?