My daughter is a senior and applying as a biomedical engineer. Should she take AP physics or AP bio as a senior?
Has she taken any Physics or Bio classes prior to Senior year? Looking at some Bioengineering curriculums at a few colleges, there is really more Engineering than Bio for the major. It may depend upon the school but I would take AP Physics.
As long as she has completed a sequence of HS bio, chem, and physics then I don’t think it matters a ton. I’d let her choose based on which she prefers, which has the better teacher etc.
For engineering I would chose physics.
Biomed (which was my minor) is typically, though not always, device focused rather than the biological processes. Physics would be a closer match, but it’s really not that important. Take whichever she is more interested/passionate about.
I’d say pick AP physics (and AP calc if ready for it) to help validate the engineering path decision.
My daughter is starting her freshman year as a biomedical engineering major. Last year she took both AP physics and AP bio. If possible take both. She was able to skip 2 physics classes and and a bio class thanks to her AP test scores. 
Most of Bio E is physics not Bio. Take physics.