You poor things. I hope all is ok, and her specialists can work out exactly what the problem is. Collapsing for no reason is a very scary thing, it happened to me a few years back, they did an ecg, had a heart monitor on me for several hours and all, in the end all they could put it down to was I was just getting over a pretty serious flu bug.
I know I scared the crap out of those closest to me, not to mention myself.
Hopefully she'll take it a bit easy till the docs can get their tests done.
Sending healing vibes xx