Here is the original item:
As all of her classmates were sharing
results (A)
Melody quietly left the room
(B) and found
a quiet corner in the hallway
(C) so that
she could see her grade without embarrassing herself in front of her friends.
You wanted to do this:
As all of her classmates were sharing results Melody quietly left the
room,
and found a quiet corner in the hallway so that she could see her
grade without embarrassing herself in front of her friends.
A comma after room is an error. And found a quiet corner in the hallway is a lonely verb phrase. When you connect such a phrase to the main clause in front, you do not use a comma.
You might want to review the rules.