photo is not deleted in shared album

Hello!

I have a shared album, which is shared with one other person. We both can add photos and delete them. Now I have one photo, which I added a while ago, deleted. It is not in teh shared album for me, yet the other person still see it in the shared album on her Mac, yet not on her iPhone or iPad. It can not be delted by her, as she doesn't own the album or photo.

Q. how can she get rid of that photo?

Thank you!

-L.