YTA, just because your ignorant, doesn’t mean you are malicious in what you thought was a good thing. Your approach was wrong. I fully understand the points you made, but you literally could’ve worded it differently that didn’t sound so dehumanizing.

Back in the early 2010s decade when my family had fish, they got too big for their tanks and my mother proposed “Let’s just dump them into the neighborhood pond.” To which I replied (which is along the lines you could’ve said) “that is dangerous for both our fish and the fish already at the pond.” Perhaps we could get a bigger tank or give them to a friend whom is dedicated to taking care of fish?”

You should apologize to her. NOT FOR THE WHOLE FISH THING, but for how you worded yourself.