Let's see if we can narrow this down some. If you are comfortable handling her, I'd like for you to do some tests.
When she has calmed down and is relaxed move to a spot where there's a flat surface at comfortable waist to eye level (table). Stand her up on it and watch to see if one or both legs offer strong resistance or if one or both buckle, which would indicate weakness.
Next, lay her on your lap and dangle her legs off to the side. Gently tap them so they move up and down, back and forth. Is there resistance or do one or both dangle lifelessly?
Next, tempt her with a treat to get her to walk. Observe her gait. Is it even? Which leg appears to be weak? Is her balance good or does she appear to be off balance and unsure of her footing?
Next, stand her up and see if her toes will curl around your finger. when you push against the bottom of her foot. Is one foot weaker than the other? Does it match up with the weak leg? Or would you say both feet curl tightly equally?
Last, while laying on your lap, gently manipulate the legs and feet in different directions but don't force them into unnatural positions. Does she flinch or resist or cry out when the leg is in a certain position. If you hear a cry when the leg is in a certain position, do not force it beyond that. This could indicate an injury.
Report your results and we'll try to interpret them and try come to some conclusions and a possible treatment.