HCG over 2000 but not sac or baby, nothing

My friend has a HCG over 2000 but the ultrasounds show nothing. When she found out she was pregnant two weeks ago, she had bleeding the day after and that’s why they were checking her levels and they keep going up. There was something in one ultrasound (found after the bleeding episode), her levels are over 2000 now and she was called in for an emergency ultrasound but they still did not find anything. We’re all so confused.

Any ideas?

UPDATE

The OB is ordering another round of bloodwork to be done tomorrow. They are saying, if her HCG goes up again then the pregnancy is in her tube. If the level goes down, she already had a miscarriage. Please keep my best friend and her family in your thoughts and prayers. Whoever and whatever you pray too. She and her boyfriend are devastated right now. It has been an emotional roller coaster the last two weeks.

Update:

After 9 blood tests, her level is still going up. 7 Ultrasounds, her tubes are clear but they can not see a sac so they believe it is a brand new pregnancy. She miscarried the original one and got pregnant again. They will do another ultrasound is about two weeks where she will be far along enough with the new pregnancy to actually see a sac on an ultrasound. She is emotionally drained and stressed out. The doctors are saying if nothing shows on the next ultrasound when something should, they want to schedule a d&e but she is not going to agree since it is pointless if nothing it there. I will update again with the next ultrasound.

Newest Update:

She went in for surgery today. They found the fetus in her left tube. She lost the baby and her tube. Her chances of having a baby just got caught in half. Please keep her and her boyfriend in your thoughts during this difficult time.