Fix "You don't have permission" in home folders
Since account "B" didn't exist when you copied that folder over, then the files would not be owned by that user.  You can do a recursive chown to correct the situation.

However, I might suggest that you use the Finder's tools to make the modifications for you.  If you select that folder in the finder and select File > Get Info (or command-I) you can then adjust the owner in the "Sharing &amp; Permissions" section to change the owner and apply the changes recursively.  To me, this approach would have a lower risk of issues cropping up later.

When she is off at college, remember that you can use Messages to do Screen Sharing.  You can click on "Details" in the upper right corner and ask to share her screen.  Useful for remote troubleshooting!