Hi there jessfromberlin,
Thanks for posting in Apple Support Communites. We understand you're having some difficulties with your daughters device accessing your shared iCloud+ plan and see you came to us from a helpful support article for this. Did your daughter have her own iCloud+ plan before joining your family? If so, did you complete the steps in the "Switch from your iCloud+ plan to your family plan" section of that article?
We would also suggest taking a look and working through the steps in resource below from your daughters device and see if she is then able to gain access to your shared iCloud+ plan.
If you don't see your family's shared content
We hope this helps.