Ok wow so much to unpack.

On the one hand, a pet in the household should be a family decision. Your husband and the GM should not be able to unilaterally decide this without you. Jerk move on their part.

On the other hand, I imagine your SD feels incredibly alone. Mom isn’t around. Grandma is dying. She probably doesn’t feel she very much belongs. You don’t sound very inclusive of her tbh. So a dog would probably be an amazing thing for her. It would make her life better. Consider the concession.

Lastly…. Stop being a fucking asshole. You threatened to abort your child over this as an emotional manipulation to get your way over the dog? Our house is probably too small for the 8 people and four pets we have, but we have so much love in it. We have had to make changes and set boundaries, but we all love and care for each other. But You are clearly in the wrong here and a mind blowingly awful person at the moment. Get some therapy stat and get your head out of your ass. You will die bitter and alone at this rate. Jesus.