Blighted ovum??

Hello !

I had a question for you ladies. I'm not sure if anyone has been through the same type of situation but last night my sister in law went to get a 3d ultrasound she should have been about 14 weeks. Once doing her ultrasound they told her they couldn't see a baby at all. She then went to the hospital to see what was going on. They did multiple ultrasounds and showed no baby just the sac they also performed hcg tests on her and they all came back negative. She did experience bleeding in the beginning of her pregnancy at around 6 weeks she went to the hospital and they said baby was fine, gave her an ultrasound and said bleeding was normal. She started having severe vomiting right after her hospital visit and it vanished maybe about a week ago. Has something like this happened to anyone? We're all very confused because she says she never got any pain or bleeding after that.