Why Does Kryptonite Hurt Batwoman?

The most obvious mechanism by which kryptonite could be a real threat to Batwoman is that it's a needed part of a much larger whole -- perhaps as a way to recreate the Batsuit-piercing gun first seen in the episode "Tell Me the Truth".

Why can kryptonite kill Batwoman?

Kryptonite has long been known to be detrimental to Supergirl and Superman. The green rock is capable of knocking them out, weakening them, and causing hallucinations if it enters into their bloodstream. All told, kryptonite is incredibly deadly to Kara and Clark Kent.

Why did Ruby Rose leave as Batwoman?

Now Rose has revealed she exited Batwoman due to an allergy. “I did find out that I was allergic to latex,” she said in an interview on the Kyle and Jackie O Show. ... In August last year, Rose addressed her exit and expressed regret that she didn't take more time off to recover following her injury.