Teammate ashe ult cancels zyra passive ?!

So I was playing Zyra and I died, but when I respawned as the plant passive my TEAMMATE Ashe's ult (Enchanted Crystal Arrow) hits me and it KILLS me in passive. I wasn't able to press Q/W/E/R to spit the true damage, the screen just went grey like a regular death - it seems like the Ashe arrow killed or cancelled the Zyra passive, which seems silly because she's supposed to be invulnerable AND because she was on my team as well.

STEPS TO REPRODUCE:

1. Pick Zyra
2. Have Ashe on your team
3. Die
4. Ashe shoots ult at you