Nah stabbing or not still pretty sure she was pregnant at the time (i.e, the not feeling well arc, being mother is hard talk, Sensei's feeling of losing something
important as well, etc) despite may or may not being the prerequisite.
If getting killed by Ami being the condition is true, that would mean Ayane had to feel the blade within the short time between being on the roof with Sensei and the actual reset while the whole time Ami was at home having slumber party.
Saying this is because if she was killed off screen way before a reset then I would assume she would start acting hectic about things way before the reset happens and not immediately after, a similar manner like Makoto in which her physical state was reverted back her instantly but mental state wasn’t).
Or maybe it’s the road killed Ami that is doing all the stabbing