Hiya, and welcome to BYC!!

Sorry it's on such sad circumstances though. Poor thing! Three months? Wow! Do you think she was living on her own all this time or that someone was feeding her?
It does appear her right ankle is swollen and that might be bumblefoot on the same foot.
I would give her a long soak in warm Epsom salt water. Inspect her for any other injuries and/or mites/lice. See if that swollen ankle feels like just swelling or if you can feel a broken bone. Maybe soaking will help you identify anything else wrong with her feet too. Then I'd make a
sling to put her in.
I would also put her on vitamins (Poultry Cell or Nutra Drench) and probiotics (Hydro Hen, unsweetened Greek yogurt, water additives) as she's probably got a weakened immune system from not having a nutritious diet.
I'd give it a couple of days of you feeding her and treating her before diving into the bumblefoot possibility but for now, you could put some drawing salve ie. PRID on it. I would also slather her feet/legs with Vaseline. I don't think she's got scaly leg mites as her scales aren't raised but don't know what else those black marks are unless bruising. Vaseline won't hurt either way. If you think it's scaly leg mites, you'd need to do that every other day for three times.
How's her poop look by the way?
So happy for you that you got Matilda back! That's quite a story!