Discussing the ONO Rule
From the first glance, according to the ONO rule(opportunity +need =obligation), none of the two women has an opportunity to help the drowning child if taken separately. Jesse, the surgeon, surely has skills and knowledge, but she has to go to work. Fiona, on the other hand, does not have necessary knowledge or first aid skills, but her temporal and liberal resources are unlimited (for this particular case). However, her clothes serve as a deterring factor, while Jesse’s clothes are casual. 
Generally, Fiona has an opportunity to save the child’s life, because she does not have to go to work. However, if we think logically, Jesse’s job is to save people’s lives, and so it would be morally and professionally right for her to save the girl because she would be doing her job (although not in the hospital and not in the surgical coat). Therefore, Jesse also has an opportunity to save the child.
We concluded that both Jesse and Fiona have the opportunity to save the child, but only Jesse has the necessary skills and knowledge. Therefore, Jesse has an obligation to save the child, even though she has to be at work in fifteen minutes.