I agree that your sentiment was right on, and that there is no need to apologize. However, your approach probably wasn't the best. She was just casually talking to you and, seemingly, out of nowhere, you say you're going to shoot her dog. That seems a bit harsh and sudden.
Having two big dogs with strong prey drives myself, along with a flock of chickens of my own, and neighbors with sheep and baby lambs, I fully understand the implications of the situation. I understand why that was your thought. A dog like that would have a field day with your livestock and possibly your dogs too. My dogs would so happily massacre my chickens or my neighbors' sheep, it's not even funny. So, I fenced in a full acre of our property for just the dogs - 6 foot chainlink, sunken 6 to 12 inches into the ground so they can't dig under it. That way, everyone is safe.
But way too many people don't understand things like that. Heck, my neighbors with the sheep are convinced that my dogs would be FRIENDS with the sheep if they ever got a chance to meet. We've tried to tell them otherwise and think we're silly. Many people think of dogs as goofy, lovable companions that couldn't hurt a fly, instead of the domesticated top predators that they are. Sure, plenty of dogs get along well with prey animals. We had a 140 lb rottweiler that loved every animal she met and didn't have a killer bone in her body, though you'd never know it to look at her.
My point is - this girl with the husky probably felt attacked for "no reason" because she never has even had a thought like that about her dog. So, now she's mad and hurt and probably still thinks you're wrong, and maybe a little scary and mean. If had been in that situation, I think I would have tried a slightly gentler tact - "Well, if you buy that house, it sure is going to be expensive to build a securely-fenced yard for your dog. If he runs around uncontrolled, he will be a threat to livestock and could get in real trouble, or even hurt or killed, so it will be important for him to be fenced in at all times."
She still might have gotten mad, but maybe it would have been less shocking to her and made her think a bit, is all.