One problem with that. She doesn't appear in the doorway like the others. Also, she does go backwards, and only has the one sound que for th whole night.
It takes a bit of time for her to appear in the right door. Just focus on keeping an eye out for the other characters and check on the right door occasionally.
If you see Sandy peeking in, close the door.
There are several more sound cues when Sandy is moving about aside from the footsteps when she’s running toward the left door. You’ll know she’s nearby when you either hear the scurrying of the rats or Sandy eerily singing “Three Blind Mice”.