I'm going to make my fiancee return her newly adopted dog
Why do you want to return the dog?
The dog is ruining our home, it keeps pooping in the house, I don't feel I can take her back on my own.
Untrained animals can be frustrating but you should return a pet just because especially one that belongs to your partner. She could be angry and not want to forgive you.
I'm not getting into an argument with her about it. The dog has been a useless bitch anyway.
Did you guys not talk about getting a dog before since you were planning on getting married? Couples are expected to make decisions together especially since it is such a bit commitment.