Sounds to me like she does know, but either doesn't want to know, or isn't ready to admit she knows...

The fact that she reiterates how she doesn't believe your marriage can work speaks volumes, her indecision is something else entirely. Its as if she doesn't want to be responsible for ending it, but telling you as gently as she knows how that she's done.

Reminds me of when someone has very little dating experience and they don't know how to break up with their partner, so they drop hints or drive their partner to do the breaking up...

I'd be much more hopeful for this situation if she said something more in the line of "Idk if our marriage will work, but i sure as hell want to try"