Firstly if you are worried then go back to A&E, but read this first!
However my ds used to get non fading viral rashes. Flat on the skin, non-fading under a glass. Exactly like the meningitis rash sometimes. They used to send him to A&E for a blood test-and it was a viral rash every time.
However the drs at A&E said that the rash is normally a late symptom of meningitis. So by the time the rash is coming out, they're clearly very ill. From that, I think it's unlikely that the rash is meningitis. Having had the rash for two days without treatment then she'd be likely to be at best unconscious.
The most likely from the sound is that it's a viral rash. If it's more on her limbs (and sores in her mouth) then it could be hand, foot and mouth potentially-which is really just a specific viral rash.
But if she is appearing more ill, then, yes, go back every time.
Equally well if you have any reason to suspect meningitis, then don't wait for the rash-it can be too late by then.
Quick check for meningitis if she's old enough to listen and obey is get her to kiss her knee. With meningitis typically the neck won't bend enough to manage to kiss her knee.
Other thing is you would expect a reaction to light. that's standard daylight being too bright, so watching TV would be an absolute no.
But as always, if you suspect meningitis, the drs would far rather see you 100 times to check and it not be, than miss the 1 time it was.