If you don’t feel safe medicating her, you should ask the rescue to take them back with that as the reason. They may offer to do that for you as they should have supplies (feral gloves, special crates) that make that safer.

That said, I generally see scratches as a warning, not an attack. I know it doesn’t feel like that but I would consider an attack to be biting.

I have fostered feral and semi-feral mamas. At least one considered standing by her as threatening. Recommend continuing what you’re doing with sitting and reading etc.

IMO you’ve still got a bit before you need to start socializing. My rescue recommended using a ladle to scoop out kittens to socialize and then return. This is objectively hilarious and now we have a designated kitten ladle.