For
sake if you have a guide dog you should get priority- Full Stop.
I agree with he other comments, this lady and her dog should NOT get priority.
There were 20 other seats and probably 20 other passengers who needed to get home to be at work the next day.
This woman and her dog and her husband did NOT have reservations, and probably no compelling need to be home that night, so the airline prioritised appropriately.
Just because she's blind, there is no reason to give her special treatment. In the circumstances, she got the appropriate service, and was offered a seat (or 3) the next day, and those more in need of an immediate trip home got it as well.