Take a good look at the leg, feel it, compare it to the other. Look at the bottom, see if there is a bite, a wound, any infection. Is the leg noticeably warmer than the other?
I would go ahead and get her into a lukewarm tub of water deep enough to float in, and do not leave her unattended.
There could be something wrapped around the leg, even high up on the leg near the body.
Is she eating, drinking?
I would make an Epsom salt compress and wrap the leg and the foot for ten to fifteen minutes at a time, three times a day. If it were me I would also dab a tiny bit of Traumeel on the foot and leg and massage it in.
Look over for any other hidden injuries - under the wings, near the vent - if she tangled with something she could have more than one injury. If you see puncture wounds, clip feathers away from the wound site and clean them with soap and water, or some betadyne and water. Vetericyn is a nice product to have to prevent infection. Be on the lookout for infection, you may need to get some antibiotics from a feed store.