UPDATE. My vanishing twin hasnt yet vanished but hasnt grown either ....
BUT I do have one gorgeous little baby that measured 9 weeks 1 day and was like a lump of jelly wobbling around on the screen. Everything present and correct and measured 23.3mm CRL with a sac of 65mmx52mmx30mm
So something to be happy about - she tried to avoid scanning the second sac as much as possible I think to avoid upsetting me. Im a little gutted as had been dreaming of miracles happening and baby growing super fast and catching up but obviously it was just never meant to be.