At risk of the dog training gods striking me dead, I'll take a different approach to the issue.
We have dog reactive dogs. General "we", although certainly I'm included in that! We don't try to make them love every dog who walks down the street. Instead, we teach them that they need to be able to coexist and that we will manage the situation so they don't need to worry. It sounds to me like Mia is "human reactive". So why try to force her to take treats from strangers? Why not teach her there is no reason to worry because she won't be forced into a situation she isn't thrilled with. Massive treats and ball and reinforcement from *you* when she is able to be comfortable around other people. Teach her she can focus on you and not be concerned, because you will be sure other people aren't going to bother her.
The change in Meg after I stopped trying to make her like other dogs and just started to make sure she never had to worry was remarkable. She walks confidently through crowds of dogs at trials and on the street now without a second glance.
Just a thought from the other end of the spectrum.
We have dog reactive dogs. General "we", although certainly I'm included in that! We don't try to make them love every dog who walks down the street. Instead, we teach them that they need to be able to coexist and that we will manage the situation so they don't need to worry. It sounds to me like Mia is "human reactive". So why try to force her to take treats from strangers? Why not teach her there is no reason to worry because she won't be forced into a situation she isn't thrilled with. Massive treats and ball and reinforcement from *you* when she is able to be comfortable around other people. Teach her she can focus on you and not be concerned, because you will be sure other people aren't going to bother her.
The change in Meg after I stopped trying to make her like other dogs and just started to make sure she never had to worry was remarkable. She walks confidently through crowds of dogs at trials and on the street now without a second glance.
Just a thought from the other end of the spectrum.