Look, just because repossessing her own body as a spectral undead that clearly can interact with the physical world anyway wasn’t a great plan doesn’t mean she’s not that unintelligent.
It just means that she has all the foresight of a can of cream corn.
I think it’s a lore oversight. In Before the Storm she chooses not to breathe when she meets Anduin at the Gathering. It’s explained as a conscious choice. I don’t think it’s so much Tyrande was choking her as she was trying to sever her head with her bear hands. Sylvanas must still feel an echo of pain or panic at her potential “death”
It’s been asked above, but it’s true. Blizzard has a hard time describing undead, especially Forsaken. You have the clearly undead like your average ghoul, skeleton, and zombie, but Forsaken seem to sit in that weird region that’s not quite undead, but also not alive, either.
One thing to remember is that Tyrande has been hopped up on Night Warrior juice. Normally it’s quite difficult to kill undead but her attacks would’ve been magically enhanced which could make the difference.
its a natural reaction to rage, anger, and animosity to want to choke someone. It appeals to the pysche of the enraged aggressor
You are assuming she is simply trying to choke her rather than break her neck. Undead or not, severing her head from her spine by crushing her neck would incapacitate Sylvanas.
Artisitic license. Don’t take the action literally.
If undead don’t need to breathe then the only logical way to kill an undead would be to completely vaporize them. Because if they don’t breathe then that dictates that they don’t need any vital organs therefore the only way to kill an undead is to beat it into mush. Which that obviously isn’t the case.