It might also be worth them getting her checked by a vet just in case she has a chip, and reporting her missing, and contacting rescues unless they are willing to go through rearing kittens, finding them homes, and spaying mum - it isn't cheap, and if she has any problems, it could get very expensive, we were quoted £500 for an emergency c-section last year. if they want to keep her, she is best either in one room or in a large dog cage, to prevent her having them in unsuitable places, and also she will need some quiet time once they arrive.