The hcg isn't wrong. If she got a positive she's pregnant. She could have had a chemical pregnancy with the first positive you said was false. That means she got a positive and miscarried very early (usually before the heartbeat appears). Unfortunately, the chances of having this type of miscarriage is pretty common. I believe it happens to 50-60% of first pregnancies, though the mother typically never knows it. But as I said, if she got positive tests, she is pregnant. I wish her luck and congratulations on the positive.
If she got a positive herself, and a positive from her doctor, it's not wrong, She's pregnant.
If its a blood test its probably correct.