Does the forbidden solitude occur if the maid is alone with one of the elderly woman's sons in the house, even if the maid opens the apartment door and sits next to him from inside the apartment?

As long as the mother is present and of sound mind, the unlawful seclusion (khalwa) does not occur. However, if the mother is not of sound mind, then no one is permitted to enter alone; because a person who has lost their intellect is not in the position of a trustworthy and capable woman, and her presence is as if she were absent, completely.