Answer:
Her nearing death
Step-by-step explanation:
The term biological clock has many different meaning, one of the is the decrease of female fertility with advancing maternal age, the other the biological program that limits the lifespan of an individual.
Rosa's grandmother Teresita is the term biological clock to the fact that she is approaching an age at which she is likely to die. Winding down means slowing down in life, closing things, being at peace with the idea that one's death is near. The term is a neutral way of saying that she is feeling old and ready to die.