If you take her to the vet get an X-ray might show something, sometimes tumors (benign or bad) are not hard to see, depends. You also might get meloxicam from them and see if that helps her.
Epsom soak - why not make it a girls’ spa evening and bring in a friend too, maybe her second in...
Your remark about weight bearing made me think of arthritis and pain. @micstrachan Are you giving her any pain meds? You might ease her discomfort, whatever the cause, with baby aspirin (1/2 tablet I believe?), or children’s liquid Tylenol (I don’t know the dose). Then see how she moves on that...
I'm no expert but my impression is she lifts her leg well. Her toes do not stretch out in readiness as she puts her foot down, and it appears she is compensating by bringing her leg high up and then more forward, so when the foot comes down in an arc the toes open up to stand on. Just an...