Se encariñaron con una mascota ajena🥹 imagino como se sintieron. Realmente tener una mascota es muy beneficiario en una parte, ya que como dices te cambian el ánimo, ya que ellos perciben tú estado y hacen lo posible de mejorarlo.

They became attached to someone else's pet. I can imagine how they felt. Having a pet is really beneficial in one way, since, as you say, they change your mood, as they perceive your state and do their best to improve it.