Pictures of the bottom of her feet will help. Usually, for bumbles that present on the bottom of the feet, you want to dress the wound with a drawing salve or antibiotic ointment (or sugardine - use the search tab). Soak, dry, ointment/salve, gauze then vet wrap. This should help draw the infection out. Do this daily or every other day.
In between the soad and dry, try to manipulate the bumble. Remove the scab and see if the infection kernal will pop out by squeezing. Chickens cannot expel infection on their own and must be helped to do so. Sometimes, bumbles on the tops of toes and or in between toes need lancing to remove the kernal.
Also - be careful when wrapping the foot. Too tight and you cut off the circulation and the foot dies. Just tight enough to keep everything in place but still allowing the foot to move freely. I like using 1 inch vet wrap.