This might not be what it is but I want to give my advice:
A few of my hens have lose webbed toes. Meaning that dirt and poop and wet things have been jammed up there webbing and have caused bumps like what you have in the picture. I would love if you could take a picture of the bottom of the foot as well as that would help deciding what it is.
On the underneath of her foot if there is a dirt thing that doesn’t look like bumble foot... press on the top of the bump and that dirt rock will come out of her webbing. The first time I did this is was a bit hard to come out but you will know whether or not it is bumble foot or not.