For that untranslated page, here's my (personal) rough translation, as my Japanese is out of practice, but:
"あの子にできないことを私にならなんにも気にしないで思うままにしていいのよ?"
"Can't you do whatever you wish with me, without worry, those things that she can't do?"
So she is basically offering herself to him as a sexual outlet substitute for the underaged girl.
Two different machine translations say:
"You can do whatever you want to me without worrying about what she can't do, okay?" - DeepL
"You can do whatever you want with me without worrying about what you can't do with that girl, okay?" - Google
But I personally think both of them don't quite get the nuance and meaning correct... Or, maybe I'm the one who got it wrong and the machine translation got it correct. Someone more adept at Japanese can clarify if this gets seen.
P.S. I only saw this because of TizzioACaso reacting to my old comment.