Behavior Inhibition refers to a temperament or personality style where social anxiety develops when an individual faced a new or strange situation. Children showing behavior inhibition tends to feel distress and withdrawn when exposed to unfamiliar people or the environment. These children tend to ignore the new people or situations and stay vigilant of their surroundings.
As per the question, Gretta become shy and distressed when exposed to new unfamiliar setting and new challenges, it is a classic example of behavioral inhibition.
Being that they are the one to cater for the kid, they hold the sole decision to make whether they can cope and take care of the kids should the chance when conceived fall within the stated 75%