Hi @ngsell ,
Thank you for posting on the Instructure Community! I apologize nobody has responded to your message until now.
While I hope this issue has been resolved by now, I thought I'd provide you with a little bit of insight for the future. I always recommend ensuring it's a supported file type, however I would also ensure that she has enough storage in her course. Canvas Admins for your school have the ability to control the storage quotas, and if she exceeds the storage quota, then files will not be able to upload correctly. You can see this information via the Files tab in your course navigation menu, towards the bottom-left of the files page (once opened).
I hope this helps a bit!
Noah