It wouldn't do any harm to bathe her feet in a weakened Betadine solution (liquid antiseptic). I had a hen with the beginnings of bumblefoot, or an infection, or just a callous. Who knows!!! Anyway, it disappeared after I put Betadine on it daily for three days. The dark spots may be nothing (even just dirt) but, as I say, perhaps worth a go.
I also had a hen with a sprain including two of her toes broken. She took a jump down onto hard bedrock and landed badly. There was no swelling, just limping and she healed up fine. Within 2-3 weeks the limp was gone. During this time, I just avoided making her run much. For example, my 4 girls come running like mad things if I call them for a treat or to get taken into the run at night (scratch time....). So I would wait until she was already close by to me, before I called. Then walk very slowly so she didn't run to get into the run first to get the goodies. That was a year ago and she shows no further probloems, though the toes healed crooked.
If you keep her as quiet as you can, but still with the others, I wouldn't worry unless it worsened. Some extra prtotein can help with healing too - mine love a can of sardines or a ouch of cheap cat food. Seems to be quite the cure all.
All the best.