^^^x2 try to communicate clearly with the neighbor and outline what you’re doing about the situation. Poisoning the puddles with bleach is going to wreak havoc on the environment! Really, really not ok. She is going to kill a lot of other non nuisance animals too.I'd make getting rid of your drakes the highest priority. Following that, you have to decide just how many you actually WANT to keep, and build a fully fenced-in pen with a roof for them that they stay in. And then keep whittling down your flock to the target number. I know they're tough to catch but you just...have to....there is no other way.
I can imagine your neighbors frustration with them in her yard - that really is your responsibility as all these offspring of the original 3 are not wild/feral
Bleach is definitely a terrible way to go about it though. I'd reach out to her and inform her that you do understand her issues and you are taking steps to remedy the problem, she doesnt need to take things into her own hands and kill the birds. If shes not receptive to that you can try informing the authorities - you're not supposed to poison any animals, wildlife or other peoples pets, and youre also not supposed to just dump chemicals into your backyard either.