Step 1: K.K. Shailaja, popularly known as "Shailaja Teacher," served as the Health Minister of Kerala.
Step 2: She received international recognition for her proactive measures during the COVID-19 pandemic.
Step 3: Kerala's handling of the early wave of the virus, with strong contact tracing, widespread testing, public awareness campaigns, and robust healthcare support, became a global model.
Step 4: The United Nations honoured her for these efforts, particularly for her leadership in flattening the infection curve in the early stages.
Step 5: Other options:
- Tamil Nadu, Karnataka, and Andhra Pradesh also took measures, but K.K. Shailaja was specifically associated with Kerala’s health initiatives.
Thus, the correct answer is $\mathbfKerala$.