As long as your mother was legally competent when she completed the power of attorney, there are two answers to your question: one based in the law and one based
on common sense. Both answers are the same"”but not likely what you want to hear.
An agent named in a power of attorney is empowered to carry out the wishes expressed in that document; it's the very reason a power of attorney is created. An agent who is unable or unwilling to carry out that legal duty can step aside and let an alternate agent act instead if there was one named. That would take you off the hook legally if you do not want to follow the wishes expressed in the document.
But you also might want to try on the question from a common sense perspective. It is unfortunate that your mother did not discuss her reasoning for not wanting to involve hospice in her final care, as that might now give you and the other family members involved some insight and solace. But the wish seems to be clearly stated"”and the fact that it stands alone in the directive seems to underscore that she felt strongly about it. Despite the fact that your wishes differ from your mother's, bear in mind that the sentiments she expressed and the power of attorney she created relate to her life and death, not yours. I don't mean to sound harsh, as your intentions sound only good and caring.
It might make your role easier if you imagine the situation reversed. For example, say you finalized a power of attorney specifying your strong wish that you'd want hospice involved in your final care, but your agent ignored that and chose another route when you were no longer able to express your own opinions.