If she mentions what your husband said, I'd just say, "that was before we realized the dog has issues that require so much time, energy and money."
I stopped reading through all the replies because they all seem to say the same thing.
I'd like to elaborate. Dogs don't forget their previous owners. I wouldn't ever let her meet my dog again. It has nothing to do with her giving up the dog either. I'm not that punitive. I don't really care about her. It's all about my dog and my duty to her.
It's too confusing. When my dogs come into my home, I give them a new name, their own bed, their own crate, new toys, new everything and they start a brand new life. I usually transition them off their old food as soon as possible unless there is a veterinary reason why I can't.
I want my dogs to know, this is your home forever, and there is no going back.
BTW, there is common wisdom that it takes dogs three months to feel like their new home is really theirs. My experience (with shelter dogs I've brought home) is that it's at least a year before they fully relax. It's the small things: the way they sleep, or the way they snuggle up to existing dogs, or eat their dinners more slowly, etc. It's even longer if the dog has behavioral issues, like anxiety.
There is NO way I would let my dog see their old owner before two years.
Well, I wouldn't ever. But certainly never before the two years are up.