This will sound a bit extreme at first, and is a bit “worst case scenario” so please keep reading for the good news at the end! 😊 And you’re right, post viral fatigue, especially only 2 weeks on is quite normal.
DS had quite a severe case of covid when he was 10, and the fatigue did take a while to go. He got ill in March, and it took him about a month until he could manage a decent walk outside, and he managed to go back to school full time in September, although he did miss days due to his fatigue for quite a while. He’s now 13 and while he does seem to get tired more easily than his friends, he’ll happily spend a whole day out playing football and wandering around town now, and goes to school as normal.
It sounds like your dd’s case was milder, so hopefully she won’t have anywhere near the same problems, but I just wanted to reassure you that even in a worse case he did recover, and nothing sinister flared up (and that’s with covid causing some heart issues for him too. That also resolved thankfully.)
Tiredness after a virus can be common, and the most important thing is for her not to rush to get back to normal, or force herself to do more than she can. That will only set here progress back. Lots of rest is good, and vitamin D/immune system boosting vitamins will help. Some people have found probiotics help too.
Hope she feels better soon!