SOC - At least hopefully your daughter will be informed enough to notice warning signs if they become significant. That's a huge advantage. Of course, she is also young and therefore indestructible, which can be tough to get around.
My original crash was at 20 years old. I had recovery, then crash, then recovery, then crash again, then a long period where I was living a normal life but my functioning was gradually and subtly declining. But I did recover enough to live "normally" (full time school, work, parties, light exercise, marriage, etc.) for many years. I was able to work until about 12 years following that first virus and crash, though eventually it became EXCEPTIONALLY difficult to do so, and at that point I'd cut everything else out of my life to do it (chores, errands, hygiene, etc.). I didn't realize at the time how abnormally ill I still was, because I'd been that way my whole adult life and I had never received an accurate diagnosis the first time around.
Looking back on it, and now having some idea of what healthy people are capable of, I can see that I was still really sick through almost all of those years when compared with a "normal" person. But I still consider it a partial remission, since I was able to do normal things with my life and the PEM wasn't as obvious (I just thought I got sick a lot). And for a while, I really did feel like a healthy person pretty much. I think. Kind of. ...Okay, I have no idea what a healthy person feels like.
But I think having this pattern with the illness makes me more skeptical of treatments and the "recoveries" they trigger. I'm never sure whether the gains are really as permanent as they make them out to be. I'm pretty certain I'm a real ME patient, and I know that I thought I was recovered. I've been looked over by some very knowledgeable doctors who support the ME diagnosis very confidently, and I've since gotten severe enough that it makes the symptoms very easy to identify. I've got all the hallmarks in spades.