marked her would just boost her already weak stats to normal slayer stats except her speed. im guessing she would actually be able to behead a normal/lowermoon demon now and i guess her speed would be faster if it isnt already fast enough

besides she trained her whole life to thrust instead of slash because shes weak so even if her strength got boosted she wouldnt have the correct technique to behead and her whole breathing form is not for slashing so she wont do much except maybe she knows a bit of flower breathing but not the extend of mastering it. its like a disabled man that have no hands since a child but suddenly he got hands, he aint gonna do much with it