Look at the first response from 'Mrs A' about stats compiled from her clinic on the number of cells in an embryo and success rates, for all age groups. There is very little difference between a 7 cell and 8 cell as far as overall success rates.
Ya, I feel for your friend though, I would not be very happy either that the others arrested. I have personally not had good luck with anything less than 8 cells, frankly (BFNs and m/c), with success from an 8 cell. The data on the 7 vs 8 cells surprised me (based on my bitter personal experience) and hopefully will be encouraging for your friend. Does she know the embryology result from the other couple in the split cycle?