My friend had a hb of 85 one week, they told her that she will probably have a m/c. The next week they went in, and the hb was over 170 and the baby was in a different position. They think the way it was laying was cutting off air supply. But the baby came out fine.
But like everyone else, theres always a possibility.
When I was carrying twins 8 weeks apart, (didnt know it) we went to the "gender" u/s and found out that our first baby died, but there was another one in there, but the HB was only 50 bpm. They said theres nothing they can do, keep up eating, take your prenatal, try not to stress.
I did all that, and i was even rubbing my belly, talking to it. Saying stuff like "come on baby, you can make it, we can do it."... but i ended up losing it anyway.

I had a d&c to get rid of two babies. Because I didnt miscarry either, they both just died. So i guess it all depends. Just tell her to keep up like shes still pregnant. Try not to cry, but prepare herself for the worst.