Refrigerator vent freezes up

My daugther has a side by side refrigerator and she said the vent in the refrigerator side is freezing up with ice. What would be causing this problem, appreciate any help in resolving this.

First check the compartment temperatures.
The freezer should be 0 to 5 degrees F.
The fresh food should be around 37 to 40 degrees F.

If OK check the door seals.
Make sure they and the units frame are clean.
Take a 2 inch wide piece of paper and place it between the seal and the frame and then pull it out to check the seal.
Work your way around the doors every 6 to 8 inches.

Check the hinge side of the door to be sure that the seal is not catching and twisting etc.
If it is then a light coating of vaseline or white lithium grease usually fixes this.