Ok, I finally went and looked at it in the management shell again - this time I did "Get-CASMailbox -identity username |FL" on the user's mailbox, and then did the same with mine and went line by line comparing them.
What I found was that almost all of the "Set-CASMailbox -identity username -OWA.....Enabled" entries for this user were set to $false except for "OWAEnabled" and "OWAPremiumClientEnabled". I went through the list and set them to true and now they are all visible for her. The strange thing is that all of those entries on MY mailbox (which works fine) and other working mailboxes I looked at didn't have an entry at all in those properties, yet still work.
If anyone has any input into why that may be, I'd be curious to know, just for my own education, but I'm going to pretty much say that this one is solved...