Not sure, but seeing as though this is a Relationshipcatogory I'm guessing it's something gross.
You can probably install the CBBE mod for female characters and then tweak the body shape using the specifically designed CBBE BodySlide tool. These can be changed at any time during the game to see the results instantly, although you may have to also install armor mods designed for CBBE.
In Wolverine Origins, he has scar tissue that completely covers his mouth. So, if he talked he would make muffling sounds. Even if he cut himself a mouth, his healing factor would kick in healing the cut; in essence, he could not talk.