Frizzlefraz, I also have not encountered or read about open wounds resulting from Marek's infection. When birds suffer from acute cutaneous Marek's-- which is when it shows up in the skin/feather follicles, it tends to look like warty, lumpy growths.
I am not saying it's not Marek's... I, sadly, have no idea without seeing your bird in person and even then maybe only lab results could tell us. If she were mine, I'd look for other reasons for her problem first, and see if I could cure them.
Her wound may be a cyst that has burst, or a problem (other than Marek's) with her feather follicles. Frizzles DO have strange feather genetics... it's actually a detrimental feather condition if they were "wild" birds. Or perhaps another bird or predator caused the wound? Do you know?
If a chicken or predator gave her the wound, you might also consider her limping to be an internal injury that is delayed in showing itself. It's hard to say.
I don't know if her wound and her sudden limping/leg problem are related or not. If you can, you might consider taking her to a vet, because it's not 'ringing any bells' for too many people here if you aren't getting suggestions. If you cannot, just keep the wound clean and treated, observe her carefully for any changes or symptoms, and consider vitamin therapy.