I didn't want to suggest one way or another a reason the priest didn't see your mother.  You know the local situation and I'm confident that you're reading this not only charitably but also correctly. A priest friend of mine, ordained more than forty years ago, observed recently that when he was ordained, if he had peered 40 years in the future, he might have expected to see himself as pastor of a large parish with three curates assisting him.  Instead, he is pastor of three parishes with no curates assisting him. (he does have a "Mass priest" assisting on weekends.)
The bishop's primary job -- almost his only job -- is to provide for the celebration of the Mass and sacraments for his people. When a member of the church requests the Sacrament of the Sick, especially as the end of life approaches, and can't access it, this is one more indication that the bishops are not doing their jobs.