How do you know if it is really a miscarriage or possible twins?

My daughter is pregnant, her last period was around Oct 9 or so.. No bleeding no cramping.. she went to have an ultrasound and they could not hear the heart beat (l or abd) so they took some blood work... For the last 3 weeks they have taken blood work and they are not telling us anything, they want her to wait until after Christmas to have another U/S and more blood work... I am fustrated and my daughter is sad, could it be a miscarriage or could it be twins and just hiding and cant hear the heart beat.. she saw a small pea on the screen and her stomach is continuing to grow.. please give me some type of advice on what to do.....Her HCG went from in the 10,000's down into the 1, 000's my daughter stated