As the dm i wanted to do somthing with this. I was thinking that her wild magic keeps it in check but when she surges she loses the hp. My real question is how does she cure it. The highest level player is 8.

The infection that the Blue Slaad inflicts, the Chaos Phage to be exact, is a magical disease and should be able to be cured with a casting of Greater Restoration on the sorcerer. So if someone in the party can’t cast it, having the party find a npc cleric or priest that can cast the spell would work.

Note though that should the disease run it’s course and the sorcerer turns into a red Slaad (or green Slaad if the sorcerer is at least 5th level), only the wish spell can restore them. 

I believe you actually just need Lesser Restoration or a paladin's Lay On Hands.  Infections by either red or blue slaad are treated as diseases, so anything that can cure a disease can remove the eggs/transformation.

Curiously, Greater Restoration doesn't work on diseases, so technically that spell won't work to cure the Chaos Phage. 

Quote from Mephista >>

I believe you actually just need Lesser Restoration or a paladin's Lay On Hands.  Infections by either red or blue slaad are treated as diseases, so anything that can cure a disease can remove the eggs/transformation.

Curiously, Greater Restoration doesn't work on diseases, so technically that spell won't work to cure the Chaos Phage. 

 Shoot, I still get them confused. You are correct. Greater Restoration was how the Chaos Phage was cured in 3rd edition but in 5e Lesser Restoration is the spell that cures diseases. 

Ah but greater restoration can cure 1 effect that reduces the targets HP maximum - and that is exactly what Chaos Phage is doing, so it will work.  Lesser restoration however, will work to cure the disease.