The fridge needs 1-2" all the way around and about an inch off the back wall. Air comes in the back panel and pushes out the front .... so it needs plenty of room to draw in. It's acceptable to have no clearance on one side and 3" on the other ... or similar situation. You just don't want it fully boxed in .... it won't run correctly very long with no cool air coming in.
As for the plastic I would need a picture. I have never seen them come with something that needs to be removed .... the white plastic panel is likely meant to stay. However if someone placed a white plastic tape type item over the grille .... that would need to come off. If the plastic your referring to is just a piece of plastic with screws holding it on .... nope it stays.
Ok. I'll tell her to leave it on. I haven't seen it either so it is hard to know quite what it looks like. If it isn't meant to stay on then I suppose the fridge would over heat and stop working? Thanks