Welcome to YT.
It's nice that your new addition to the family has bonded with your daughter and feels protective of her, but you are right to want to stop the guarding behavior immediately.
I have seen episodes of "It's Me or the Dog" and "Dog Whisperer" in which Yorkies and Chihuahuas were overprotective of their primary humans. Both trainers employed repetitive exercises where they would sit next to the protected person and put their arm around the person. The dogs would bark like mad and try to jump on the unwanted person.
Essentially the exercises were intended to desensitize the dog through repetition and not giving in to the dog trying to push away the unwanted person. Both trainers put their hands, or had one of the people in the exercise put their hand on the dog's shoulders and make sounds to communicate to the dog that the behavior is undesirable, like "ah, ah, ah" or "shhhh" or "no."
You could also work on training the dog to obey commands like "sit" and "down." Use small treats to reward the dog when he is calm and obeys commands when your daughter is being hugged or kissed. The "unwanted person" could be the one to give the dog the treats.
You may also consider hiring a professional trainer to come to your house for a few sessions. The right trainer could help make your dog somewhat of a service dog for your daughter in a wheelchair.