Final answer:
The next step after an initial assessment of a child who has ingested unknown plant leaves is to contact a local poison control center or emergency medical services, as they are equipped to manage such situations.
Step-by-step explanation:
The appropriate first step after completing your initial assessment of a 3-year-old female who ingested several leaves from an unknown plant would be C. Contact a local poison control center or emergency medical services. This action is crucial for several reasons. Firstly, professionals at a poison control center are trained to identify the risks associated with various substances and can provide specific advice for the situation. Secondly, the unpredictable nature of plant toxicity and the potential severity of the effects on a small child necessitate a timely and informed response. It is not advisable to wait for symptoms to appear because some poisons may cause damage before symptoms are noticeable. It is also not recommended to administer any substance or antidote without professional advice, as this could cause further harm. Conducting an experiment to identify the plant by taste is dangerous and should never be done.