I wasn't able to find that much about the Asynja, but here's what little I did find: Asynja is not a specific deity, but the word for a female Aesir, one of the two pantheons of Norse gods, along with the Vanir.
Since the Allfather is Odin (who has a lot of names, including Wotan, whom I mistakenly thought was another deity), it might make sense to associate the Asynja with Frigg (or Frigga), the mother goddess and wife of Odin. Frigg and Freya are closely related, and may in fact be different aspects of the same deity. Frigg was considered queen of the heavens, the goddess of motherhood, fertility, love and housework. She was reputed to have the ability to forsee everyone's destiny without revealing it. She owned a necklace, the Brisingamen, which, besides making her irresistable to man or god, gave support to any army which she favored on the battlefield. She also possessed a cloak of feathers which allowed her to change into a falcon, or into the battle-boar Hildisvin (which she is also described as riding). She chooses half the slain on the battlefield, whilst Odin gets the other half (is this the justification for the Allfather's death magic?). As Freya, she also practised Seidhr, the form of magic practised by the Volva. There is speculation that Gullveg was Freya under another name, and if so, she was stabbed and burnt 3 times, but arose from the flames each time and transformed herself into Heidhr, the Glorious, mistress of magic. This started the war between the Aesir and Vanir.
Whew. Confusing stuff
But out of it, I can come up with some suggestions. 1) Give the Asynja some nature magic, since she's a fertility goddess. Problem is she basically becomes a Mother of Tuathas
2) Give her the ability to avert bad events, since she foresees destiny, and practises Seidhr. Not bad, and especialy thematic for Midgard. You'd probably even want to change her path to Astral. 3) Give her a standard, since she owns the Brisingamen. 4) Depict her as riding a great boar, and give her trampling. 5) Let her tranform into a falcon. 6) Make her immortal - but I don't know that Dom2 needs an immortal titan-class pretender
I rather favor changing her path to 2S, or possibly 1S1N, and giving her a standard effect, while removing the glamor. It might be a bit much to give her bad luck prevention as well, but it might be thematic. She should remain a mighty warrior, as all the Aesir were apparently gods of war.