What could this be?

[lollipoprainbow]

Dd10 had a bit of a headache last night, we'd had a busy rushed day and she hadn't eaten much so I put it down to this. This morning she is extremely hot temp of 38.5, really bad headache and feels sick but hasn't been as yet. Her Covid test is negative. Could it be a migraine? I suffer from these too.

A migraine wouldn't raise her temp that much. It sounds like some kind of virus, possibly Covid. I would test her again tomorrow and in the meantime give paracetamol and encourage her to drink plenty. Covid presented like his with my DC ages 10 and 12. Severe headache, fever and nausea (and tiredness) were their only symptoms really.

@BlackInk thanks that's my first thought too, can I ask how long it lasted?

Both DC had headache and fever for 3 or 4 days. DS was sick once and DD was just nauseous for a day. They did test positive before these symptoms started though – DS was picked up by a random LFT for school and his symptoms started a couple of days later – DD had a mild sore throat and tested positive with headache/fever starting later the same day. However, I had mild symptoms for about a week before testing positive (coinciding with symptoms worsening).
Your DD could have another virus. Could you LFT her again and be super thorough with swabbing?

Both my children started feeling unwell with a headache, nausea and high temperature over the past few weeks before they started with chicken pox.