Still syringe feeding 2 weeks after cold - How long will this last?

My 14 y/o girl had a bad cold and stopped eating two weeks ago. The Vet checked her out then and said no infections. He prescribed Orbax for a week as a precaution. Because of her appetite loss, I have been syringe feeding her for two weeks now. Her symptoms have improved dramatically - very little congestion and sneezing. Her energy level is up although still not behaving like she used to. The big difference is her loss of appetite. She seems interested in food and sometimes eats a very little bit on her own. Once I see she is not eating what she should, I use a syringe to feed her which she seems to handle well. I try to get a 5.5 oz can of a/d into her daily and mix L-Lysine in with the food twice a day as per the Vet's advice. He also offered to put her on an appetite stimulant which has not been done yet. I spoke to him yesterday and he said the recovery could take a month or so.

I've tried offering different wet foods (Baby food, Friskies, Wellness, Max Cat) with the same result. There was one day last week where she seemed to eat well on her own and then reverted back. Any thoughts or encouraging words as I'm concerned this is a losing battle. How about the appetite stimulant? Good or bad idea?

Thanks

The herpes virus can cause mouth ulcers, which are extremely painful.  The vet did not see any of these?

Did the vet take blood?  A lot of systemic illnesses can cause lack of appetite. 

He checked out her teeth?  How about an x-ray?  There may be a problem that is not visible to him.

One of the side effects of Orbax can be loss of appetite, but it does seem that after a week of being off of it that her appetite should have returned.  I agree with LaurieA that perhaps there is another issue?  However, is she still a little congested?  If so, maybe it would help if you slightly warmed up her food so she can smell it better.