Give her permission to post the pop songs ONLY IF she includes an explanation in the post why this is significant for the Philosophy group.
She can post the lyrics, ask a question that the song inspires her of that is Philosophical, something like that.
Perhaps reminder her that the Philosophy group is more about words than videos and we need written words to work with.
This allows her to continue posting them if she wishes but also respecting the group’s preference to having words and sentences to respond to.
In addition, she could be reminded that not everybody has a working video player and expecting everybody to have the same access to video content is not fair to all members.