Dogs, even friendly ones, are unpredictable.
My aunt has a dog who knows me relatively well. The dog was rubbing against me, I was petting her, rubbing her belly and talking to her inside the house.
I had to go outside to move my car and at the same time, my aunt let her outside to do her business. I got out of my car to go back inside the house and the dog started viciously barking at me. I spoke to her thinking once she heard my voice, she would recognize me and back off. She didn't. I backed away from her and managed to get back into my car before she lunged towards me.
They finally called her back inside and that's when I was able to go back into the house. When I saw her inside the house, she was friendly towards me again. No trace of the vicious dog who had just scared the bejebus out of me.
My aunt found it difficult to believe that her dog acted this way towards me. BTW, this dog is a mutt and not a breed one would normally be wary of.
So don't ever underestimate a friendly, beloved family pet and don't judge this lady until you hear her side of the story.