This is a sad time for You, your family and for Poo.
Your video shows how distressed Poo is.
Many old dogs will bark for no apparent reason - and dementia is very common. Does Poo still have her hearing? Many dogs vocalise like this, due to the dementia, but are unaware that they are making noise!
Be careful with Meloxicam. It is a great drug - but should not be given on an empty stomach, or it will cause gut problems. If her stools are black, or very dark - stop the medication immediately.
As others have said, euthanasia is the best option here. She may not be 'suffering' , but she has no dignity like this - and her quality of life is very low. After 15 years together, this is not the way you want to remember her.