guinea pig ?

Question
I've had my guinea pig for about four years now, I got her as an adult at petsmart. She has always been kind of skidish. But would let you hold her. She hasnt been really eating lately. For the past three or four days not at all, and will not drink. We gave her some celery and lettuce to see if it was just the food. She took a bite and turned away. She will hardly move. We put a cold water bottle in her cage and she has been laying against it. She has been laying in one spot now for about 8 hours, i put a fresh cold bottle right by her and put a rag over her, she has been panting. I do not know what to do. Please help asap.

Answer
Is she overheated, that you put a cold water bottle in her cage?  I'm not sure, I get that part.  In other words her lethargy is more than
an effect of the heat.  Have you held her and checked her for injuries or pain?  Is she pooping?  I don't really know what to tell you
except that her age is advanced for a piggie.  I don't want to say to look for the worst possible outcome but, I would just hold her
and keep her with you and let her know that you love in just in case these are the last few days or hours that she has.  
I have experienced both life and death with my piggies and I would just try to make her comfortable and feel loved.  
I hope that I am totally wrong.  Either way, give her lots love and hands on affection.
Cindy