Game doesn't start with single cc

Hello there.
A friend of mine has a really big and annoying problem.
Her game was working fine until yesterday.
The game didn't start anymore so she tried to delete her mods, tray and save folder.
No matter which folder she puts back in the game doesn't start.

That's what she also tried:
Reinstalling the game, deleting the sims 4 folder so the game generates a new one.

The strange part is: No matter which single CC she puts in for testing, the game doesn't start up.
That CC, for example, was a skin. She even tried to test a new hairstyle (mesh included).
If a single CC is in the Mod folder, the game doesn't start up and she's pretty devastated.

If she tries to copy her saves folder back in, the game also doesn't start, same with tray folder and, as mentioned above, same with mods folder.

So what's going on?
That doesn't make any sense, eventhough everything worked before.
She didn't change anything, she saved the game and after that this all happened.

The drivers are all up-to-date.