What should the questioner do regarding her daughter's kindergarten in Bulgaria to ensure her daughter eats halal food, considering she does not know whether the people of the country are People of the Book or not, and should she lie to them again about her daughter's allergy to meat and chicken?

The basic rule for slaughtered animals is prohibition. It is not permissible for a Muslim to eat what has not been confirmed to have been slaughtered according to Islamic law. When there is doubt about the slaughterer, one considers the majority of the people in the locality. If they are People of the Book, then it is permissible to eat. If the slaughtered animals are not permissible to eat, then similarly, the broth cooked with them is not permissible to drink.