-Hp +Res or -Res +Hp Ophelia?

They are almost the same. +RES would be better if doubled by a mage or priest, but you should avoid anything that doubles her; +HP isa bit better otherwise.

I'd definitely choose +HP if you plan to use her in AR, as with that boon she goes over 40 HP, which is the initial threshold for some structures effect.

If you're putting her on AR def then -HP might be better because it's harder for galeforcers not to OHKO her, which can create issues if they need heavy blade to activate