Thanks, all. I guess we're going to try it with some reservations. She does have a high heart rate, but that's nothing new. I'm guessing at some arrhythmia showed up on her EKG. She has been complaining about occasional trouble getting a deep breath lately, so that could be arrhythmia, I suppose.
Based on what you all have said, this could be a good med for her as long as it doesn't give her any side effect trouble. Her BP runs low, so we'll have to watch for that. And her thyroid test results are okay, but marginal, so we'll have to keep an eye on that, too.
She's been in remission for about 10 months now -- that is, she has been able to live a normal life without PENE, or meds for ME/CFS symptoms (until now). But she's working full-time (as opposed to being a student) this summer, which is a different challenge to the body. To me, she's a good case for the idea that we can significantly improve our condition with this illness, but we can't cure it (yet, anyway). She looks, acts, and feels fine, but there's still some weirdities going on in the background.
Thanks again, everybody!