AAAAAAAAAAAAAAAAAAAAAAA

-res +hp is probably your best bet.
It won't compromise her atk spd or def

Some awkward IVs indeed

I could see any of those IVs working, but +HP -spd is definitely not preferred. Between the rest it's all a matter of what you plan to do with her, which opponents you want her to defeat. For example, some people don't care about her res so they'll give it up in favour of stats that matter when fighting non-dragon melee opponents. I personally like her res, so I wouldn't dump it unless all my other options were inferior.

A lot of people will see -spd and jump to the conclusion that the IV is trash. She still has 39 spd with the prf, which is fast enough to block a lot of doubles but not to achieve them against fast opponents, which means, due to her prf effect deactivating if she gets swarmed, that she becomes QR reliant, which means you would be locked into some build that uses QR and some mechanism for maintaining the QR threshold.

+def -atk is another odd IV, and a lot of people would be scared off by -atk. Her atk isn't that high to begin with so it will restrict her, but she can get 21 atk from her weapon (16 mt + effect) and she hits the lower defensive stat of most units in the game (adaptive damage vs ranged, and most melee units have lower res than def) so I think she's still very much in business even with -atk and not necessarily dependent on a buff; in fact, she hits harder than unmerged Nowi and Fae (exception being Nowi using flametongue).

If you interpret her as a tank first, which I do given her defensive spread, then I think I reject -res and I try to decide between some potential issues with her atk and being locked into a QR sustain build. If you interpret her as an attacker who also has bulk, then I don't think you can give up atk or spd so you go +HP -res.