After 40 years of owning cats, I've learned a few things after losing some of my favorites to "fatty liver disease", etc., way before their time: It's all about diet.
1) Feed her different food,
2) make sure you have added fiber into the food- such as pumpkin and greens (but not onions). Some cats like cantaloupe.
Problems with commercial foods:
I currently have 3 cats around 15 years old and found that they started getting digestive problems around the same time because of the additives and wheat products added into commercial foods (even the high quality "healthy" foods).
Felines are carnivores which are now being feed primarily grain based products -- this is causing diabetes, fatty liver disease and other organ aliments which they never got before. They, like humans, can also develop food allergies to these ingredients which is one of the primary causes of constipation.
My cats coats and eyes now look great, but I make my own cat food. ***
The instructions below may seem laborious, but it has kept our pets healthy and in better condition than they were several years ago. They've lost fat and gained lean body mass despite their ages which is also sort of unusual. Once you buy the products and get the routine down -- it's really painless.
Recipe for Cat food:
1) Cook 1 lb of turkey burger (preferably non-commercial - no additives - whatever is on sale works just fine!)
Put 2/3s in a bowl and put in the refrigerator after it cools. You will use this in 2 more batches of food (see recipe below) when the 1st batch runs out.
Mix the remaining 1/3 with:
1/2 can of pumpkin (go to the outlet store),
barley grass (Barley cat),
Udo's choice Pet essentials for cats,
Nu-pet grandular greens,
water, and if I remember, I also put digestive enzymes and pro-biotics (friendly stomach bacteria) into it also. What ever is around the house in the form of human supplements seems to be fine.
Mix the quantities based on recommendations on the bottles, but a little less since you're adding several brands of similar items.
Canned cat foods have HUGE amounts of salt, so although I'm not crazy about it, I'll also mix 1/2 can of commercial (Natural Balance) cat food into the glompy mess because the cats are spoiled and like the commerical food (I've always wondered if they put MSG in it...!?).
That's it for the main mix. It's not an exact science, just experiment until you find something your cat will like.
Finally, at the time of feeding, I also mix a bit of defrosted frozen RAW chicken (Primal Frozen Nuggets) into it also since they seem to like it and it's more MEAT.
My commentary:
You make a big bowl full of food which lasts for days, so it's a pretty easy process. Although this may cost a bit more after being faced with huge vet bills (like we were recently due to digestive problems on two of our 3 cats), it's not than much more over the long run. We shouldn't be feeding our companion pets cheap food anyway.
Other fiber options:
If this recipe is too complicated or expensive, you can also mix human commercial powder fiber products like apple pectin into commercial cat food - add a slight amount of water, since cats don't drink enough generally. It is an immediate fix to constipation, but doesn't solve the longer term problem of poor diet which leads to chronic disease and contributes to arthritis.
And finally, a product called Lactulose saved one of our cats lives from severe constipation; but I understand you should not give it to cats for prolonged periods because it may cause pancreatic problems.
Sorry for the long winded answer!! Hope it helps someone. Wynn

My cat "Boudreaux" has great sucess with Lax'Aire for his constipation problem.