Sometimes our pets just don't accept our partners.
If you're sure that your partner has never damaged your pet to cause such reactions, there might be a few more reasons for it.
Let's look closely.
If your partner is relatively new to the dog's life or has had limited interactions with the dog, it may take time for the dog to warm up and feel comfortable around them.
Dogs are highly attuned to human energy and body language.
If your partner displays nervousness, aggression, or unfamiliar body language, it can trigger an uneasy or defensive response from the dog.
If they sense any potential threat or discomfort from your partner, they may exhibit defensive behaviors as a way to protect you or assert their dominance within the household.
Dogs rely heavily on their sense of smell, and unfamiliar scents from your partner, such as perfumes, colognes, or even unfamiliar pets, can be unsettling for them.
If your partner is perceived as a threat to the dog's access to those resources or to the dog's relationship with you, they may exhibit negative behaviors as a means of protecting what they consider theirs.