I owned a nanny cooperation in a large city. And I'm a mom. Choosing the right nanny is such an important decision and so many variables play a factor in this decision. One of the first, and most important...is your mother's intuition. What is your gut telling you?
Your comment that concerned me the most related to her ability to act swiftly and in haste, should an emergency arise. Personally, for me, I would be choosing who could provide my child the most well-rounded care, and that includes being able to perform infant CPR with the ability to exit a building quickly and efficiently. I believe there are zero compromises when it comes to care for our children. You do a background check, driver's check, call many references, and you listen to your gut. And you know that you know that you know...that in the event of any emergency, your precious child is in the absolutely most excellent hands. Hands that would rival your hands.
Over my babies' toddling years, they fell down at times and busted open a lip, or a nose. I had to pick them up, crying and bleeding and carry them to get help. How will she fare carrying a hefty two year old? Just some thoughts. My heart goes out to you and to her too.