Hello, my name is***** and I have over 20 years of experience as a veterinarian. I can understand that you would be concerned about Lola's suddenly being unable to normally bear weight on her right rear leg.
Is she able to place the leg normally, it just won't bear weight and the leg collapses, or is she carrying the leg?
What was she doing before this began? Sleeping or awake? Or do you not know?
If you pinch her toes on that foot can she feel it?
Possible reasons for what you were seeing include a temporary loss of nerve function due to nerve compression. If she was sleeping on a hard surface or in a strange position before this began pressure on one or more of the peripheral nerves that control the leg/paw may have been compressed. This is similar to what happens to us when we get that "pins and needles" sensation in our leg or foot and cannot walk properly. This should resolve in a relatively short (less than a couple hours) period of time.
Another possibility is a condition called FCE, fibrocatilagenous emboli, where a chunk of cartilage breaks off and lodges in the blood vessels that supply the spinal nerve roots. It is very painful initially as blood supply to tissue is blocked off. The pain only lasts a short time, less than a few hours to a day, but the weakness from the nerve damage it causes it can last for a few weeks, or in rare cases is permanent. It really depends upon how severely the blood supply is compromised.
Also possible are spinal cord neurologic problems, such as an intervertebral disc(s) (cushions between the bony vertebrae) that are out of place or spinal arthritis putting pressure on the spinal cord or even a mass in or around the spinal cord.
A fracture is possible too, especially if there are any swollen areas in comparison to her left rear leg. In an older dog a fracture can be secondary to a tumor or metabolic diseases that affect calcium levels.
While I too would be concerned since she is eating and doesn't seem overly painful now it seems reasonable to confine her tonight and take a watch and see approach, make sure her beds are very well padded and have her veterinarian take a look at her tomorrow if she is no better.
Please let me know if you have any further questions.