L.L.
I would have to agree with the other comments. Sounds like one is her heartbeat and the other is the baby. I had twin girls. They did miss it the first time on the heart doppler. But they really don't know there is two in there until an ultrasound. I went in for my first ultrasound really early because i was experiencing a lot of pain which to me wasn't normal since I had carried three kids prior to full term and didn't experience the pain. That's when I found out that I was having twins. Through my whole pregnancy I only gained forty pounds. I had two full term healthy baby girls. Tell her to stay calm and congrats either way.