In the words of Linda Smith and her daughter, Hannah:

It is easier to change policy than biology.

I can't imagine a professional nurse who is not working to develop and
implement theory-driven, research-based policies. Anything less is considered
unprofessional in current nursing literature. What theory/conceptual
framework and what supporting research does this nurse manager use to support
current unit policy? Ask her--in writing--with a notation that copies are
being sent to the VP of Nursing, the Quality Improvement honcho, the hospital
administrator, etc. You can be gentle yet assertive, e.g. curiosity as it
conflicts with research reports you've read, etc.

Good luck. Theoretically this is a sound suggestion!

Karen