CAT PROBLEM!!!! HELP PLEASE

OK... I have just spent about 2 hours looking up anything I could find on Hairballs, with not much luck.
We have always had outside cats...never an inside cat until this year. So I know very little about cat problems. Our outside cats pretty much took care of themselves...they were never sick.

OK this is the problem. Maw Maw is a mouser!! She brings mice, rats, chipmonks, birds up to the front door lets everyone see them, then takes them off and eats them. @ days ago she came in and was coughing...kind of a choking cough. This went on all day and night, but she was fine otherwise. She ate and drank.
Yesterday she spent ALL day and night in a chair. Last night we tried to give her meat...nope, we tried water...nope. My hubby took her to the litter box...nope, she looked at him like he was nuts, and ran back to the chair. I have been checking on her off and on all day..she is still in that chair, refusing food and water.
Could it be a hairball, or do you think it is something else???
I just don't know what it could possibly be. If she is no better by Monday, she is going to the vet as soon as he opens.
ANY HELP would be greatly appreciated.
Thanks!!
Sue