She would be able to manipulate her bones in multiple ways such as; enhanced regeneration, rapid growth, shape and density alteration. Basically she can manipulate her bones to attack and defend with and mend them extrordinarily fast for a human.
Her weakness would be a lack of control over bones that have been seperated from her main skeletal structure. As such, bones broken inside her body would be extremely difficult to get out (due to her connected bones regenerating) and even pose the danger of piercing her organs due to the regrowing bones pushing them away.
Also, she has no real defense against any type of magic or mental attack, making her quite vulnerable against creatures with magical abilities.

As for the reason the D.I.D wouldn't kill her, I was thinking of asking if she could be created by the government's research department.
Otherwise I'd like to say she has a burning hatred towards demons due to an implanted memory that her family was killed by them.