Even though -Def mostly rules out the possibility of a Vidofnir tank set, she can do other things. While it requires a bit of feathers, you can give her Life&Death and a Firesweep Lance and she'll work just fine considering the fact that she has about the same stats as Cordelia just 1 point less attack and 1 point more speed. And you could still run a tank set since we have close Defense and Defense +3 sacred seals that can restore her Defense to it's usual numbers if you already have a Firesweep Flier like Cordelia.
Congratulation for your acquisition ! Good Tana is good :)
The IVs isn't the greatest but for sure isn't the worst since she wouldn't tank much physical damage anyways. I mean, she does tank damage but once, not 2 or 3 times, so Hp has the same value as Def.
You can build her with the firesweep build which is the most powerful one imo. Firesweep+, L&D3, Hit&Run, Guidance3