You/she may have already tried, but posting just in case these are of any help:
Rear Liftgate Is Open and Not Moving
Another problem happens when the liftgate of the vehicle is in the open position. It does not want to close. This can be a problem if you are on the road and trying to get back home. Here’s what to do to fix this problem.
Locate the close button on the rear liftgate door. It is only accessible in the liftgate door jamb when the liftgate is in the open position.
Press and hold that button for a few seconds. You should hear it beep about four times.
Release your finger.
Then, press the button again quickly to signal to close the door. This should fix the problem and allow it to close normally.
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Here is a service bulletin about liftgate issues:
http://media.fixed-ops.com/toy_servicebulletins/sb0091t12.pdf
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Probably not the issue but has anyone checked the fuse?
My owners manual lists it as fuse 21 (30Amp) Power Back Door under the hood
And the other obvious thing is the back door switch in the glove box.
As you can not manually open the back door something is jammed and is most likely similar to what sweeneyp posted
Might try pulling the fuse and see if it will allow you to manually open it.