I am sorry to hear about Molly. I have a 5 year old Frenchie boy. Don't know if you are aware but a Frenchies lifespan is usually 5 years, so Molly is doing well to have reached 6. I have never had a Frenchie live past 5 1/2.
One thing I have noticed with Frenchies and also with a lot of old buns is they often go into chronic heart failure. I would take her to the vet and see if this is the case with her. It may be possible to treat her if its not too advanced or there be another problem causing her symptoms, which again may be treatable. I don't want to sound negative, but its also possible that she has just come to the end of her lifespan. Is she definately a Frenchie - she does look more like a German or crossbred lop in the pic, but maybe its the pic.
You could try her with some herbs such as corriander, rocket, basil, mint, etc as they are very succulent and quite tempting to buns. Maybe try making her some porridge or even just the dry oats. I really think that given her age she should see a vet though. I hope she pulls through.