What happens to existing photos when joining family sharing?

Hi

My gf has a 50gb iCloud plan which is full with photos.

Ive set up a 2tb storage plan and added her as a family member.

If she joins and uses the 2tb family storage, what happens to her existing 50gb of photos?

Apologies if this is a dumb question but I’ve searched and can’t find an answer.

Cheers