Attitude towards the House Mother in a Dormitory

Hello and blessings to the honorable shlita. The situation is a dormitory for Haredi teenagers who do not live in their parents' homes but in a Haredi dormitory, known as children from welfare families. As part of the activity, the place is managed by a Haredi house father and house mother. The question arises on Shabbat when the house father and house mother are there during Shabbat. One of the children does not want to say "Gut Shabbos" to the house mother, claiming that it is forbidden to speak with a woman and also not to sit at the Shabbat table, as he believes she is not modest enough. I will add and emphasize that this place is for children from families who are unable to raise them, and the children's stay throughout the year is in the dormitory, which means they very much need the help and support of the house father and mother. I would appreciate it if you could pass the question to our teacher, the rabbi shlita. The child says he is not willing to listen to anyone else but the rabbi. Thank you very much, I would appreciate a response as soon as possible (preferably before Shabbat so there is certainty and Shabbat passes pleasantly). Thank you very much.

Hello,

According to the instructions of the Gaon, Rabbi Avraham Fried, shlita

One should say 'Gut Shabbos'.

And one should sit at the Shabbat table with everyone, and be cautious as much as possible.