What kind of cow is she? Dairy breeds can pump out so much milk they literally become weak and wobbly if they are not getting enough groceries. They can get ketosis before and even after calving, although I have seen more before calving. How much weight has she lost?
A bit is normal, emaciated isn't unless she is an extreme milker not getting enought to eat.
Did this cow have any sort of injury lately that might have effected the hips? Was she doing this right after calving? sometimes there is an injury in the calving process and it may take a while to get better.
I have seen and heard of needles given in the wrong spot effecting cattle, where a nerve is effected, took weeks for the cow to get better.
Walked with a sway in the rear end and didn't have proper control of the hind quarters for quite a while
Have heard from a lady once who gave a cow a needle and the cow went down and never got up.
Does this cow have any other symptoms or just lays down alot? First thing I would try would be getting more feed into her, maybe a bit of molasses on top to give her a boost, or ketamalt "down the hatch"
One dairy farm where I worked had a cow that didn't want to get up. Vet checked her over they thought ketosis, but treatment didn't help. A second look revealed foot rot in all 4 feet, that had gone systemic. (into her body and was killing her).
Check and see if this cow has a fever, might give you an idea what you are dealing with.
A little chat with the vet might be in order.