So, in-canon the Aragami are invincible to everything that isn't composed of Oracle Cells (which the Aragami themselves are) due to the way the cells congregate. Put simply, you can cut/smash/puncture the Aragami with normal materials, but their cells will just float back into place because MAGIC BIOLOGY. The only way to counter that is to use a weapon also composed of Oracle Cells, which will cause the damaged cells to sort of de-bind from the Aragami. On top of that, the only way to kill an Aragami is to remove its core, which causes the remaining Oracle Cells to disperse into the air, only to form more Aragami.

For the sake of her not being an invincible tank, we'll go with something a bit different from canon. Any damage short of actually removing body parts can knit itself back together in a minute or two. A removed limb that isn't lost (sent into space, left behind in a universe jump, pulverized into pus, or what have you) can be reattached in a bit more time - we'll say five to ten minutes. Otherwise, limbs can regenerate slowly over a couple weeks, which can be expedited with fresh Oracle Cells (which are contained in small quantities in O-Ampules) and by eating large amounts of things, lowering it to a minimum of a day to regenerate an arm or leg. Core removal will remain the only way to kill her, though what that would require without a God Arc or Aragami will need a bit of thought.

I'm just pulling numbers out of thin air, so feel free to suggest changes.