As so many said, there’s something which smells off in this story. IMHO, it could have been at any point in the narrative, from the passenger herself to the flight crew to the other passengers around her.
A flight attendant [presumably from another airline] said:
It’s against regulations to put an animal in an overhead bin. I’m flight crew so I know. Every LIFE must have breathable oxygen. And any animals in a cabin must be entitled to an oxygen mask at a bar if seats. I’m appalled and saddened. Thank goodness it wasn’t a baby. The flight attendant should be fired over this. Causing a death by failing to comply with federal regulations as they are trained to enforce.
Another American wrote:
I find it highly unlikely that the entire flight crew and all the passengers seated nearby allowed this to happen and didn’t check on the dog once. More likely the owner decided to put it in the overhead bin and is now pointing fingers at the flight attendant. If she was truly forced to put the dog up there I’m sure the rest of the plane would have heard the exchange between the passenger and the staff so someone would have checked on it.
If it’s taken at DM face value [always a dangerous thing to do], then the woman is simple – a child, a baby and an expensive pet she never checked on?