I'd take her, just to check the ears and the throat. If they are clear then you're already doing all you need to but at least you'll know for sure, KWIM? The other thing to do is keep her fluids up. With the fever she'll have increased risk of getting a bit dehydrated (I know you said the nappies are fine, so this is probably irrelevant but JIC!) so fluids are pretty important.
Natty had a mystery virus last year that was 4 days (and 4 horrible, horrible nights) of high temps. She was miserable too, so I kept the neurofen up to her. The Dr told me her ears were clear so there was nothing we could do but wait it out. She said if she didn't seem responsive and didn't have any "spark" to her at all, then to bring her back. (Possible dehydration.)
After 4 days she was maybe a little tiny bit snotty, but that was it! Nothing else wrong with her. Still don't know what that bug was about.
I hope Jazz is much better soon.