Thanks for the tranlsation! The tsundere brothers have struck again.
It's surprising that her muteness is psychological, and curable. Very surprisingly that her father knew about and deliberately cut off her potential, by silencing her and not teaching her to read. You would think he would try to use that incredible power, but he may be scared that it would turn against him since he treated her like garbage and all.
Hopefully they have the marriage ceremony soon and they both start to heal. Our MC is extremely paranoid, he didn't have a nice childhood either and I think they could really be a good thing for one another.