Boaz

Not a wait and see. It is a bacterial infection in the foot pad, usually in through a small cut, and it gets worse rather than better on its own. A vet can advise on cleaning and draining it. Get her onto soft clean bedding either way, because the hard ground is part of how it started.

Catch her at night on the roost, which is the only sensible way with guineas, and work from the foot upwards. Bottom of the foot first: swelling, heat, and specifically a dark scab in the middle of the pad, which is bumblefoot. Then the toes for cuts or anything wrapped round them. Then legs and joints for swelling, heat or bruising. Then the leg scales, raised or crusty meaning mites.

And compare everything with the other leg. Half of what looks wrong on one foot turns out to be normal once you look at the pair.