Willow, my 14.5 yr old turned super picky about 5 months ago. She used to be happy with kibble and some canned food mixed in. Now, I give her a cup of kibble and a cup of something yummy I buy and cook especially for her: steak, meatballs, liverwurst, pork chops, beef liver, hamburger meat. Just over the past few days, even those things are not interesting her so much (she will go nuts over cookies, though).
I'm not really concerned with how 'bad' something may be for her, I just want to her eat *something*. Lately, I have dolloping a little bit (maybe a tablespoon, total) of canned cat food over her meals. That stinky food is enough to get her interested and she will usually finish her bowl of food (sometimes it takes 2 attempts - she'll eat a little, and a few hours later come back and finish). I know its not the best thing, but at least she's eating and her stools are normal.
Its worth a try.
Good luck with your senior girlie.