Export with ios Mail app or ios Gmail app (mycloud location)

Hello all,
I own a mycloud mirror Gen2, fantastic device. No problems whatsoever. Although I shared a folder with my wife in order to use it with her. I installed mycloud app on her ios phone and all work fine. Except a detail that works for me (maybe because I am the admin and folder owner). When she tries to export a attached file (PDF file) from her ios mail app or gmail app, she chooses the mycloud icon as destination, but when she picks the location to export the file, it never browses the shared folder. It happens both on the Gmail app and ios mail app. If the goes directly to the my cloud app, she can export a photo to the location (but only photos from the photo stream or album). Does anyone have this issue with shared folders with other users ? She has of course a Mycloud user in order to configure the mycloud app and access my shared folder (with read and write permissions).

Thanks for your attention and I hope I could explain myself well.