For starters - no, her passive cannot be resisted.

If your goal is to use her in arena, I would say you have two options. Personally, I use her on my speed nuke team to prevent revives, but I also use her on my go-second team depending on their comp.

If your goal is to use her mainly on your speed nuke team, then put the focus on accuracy, as her main job will be to do the DEF down and Weaken. If your goal is to use her on your go-second team, then put the focus on resist, since her main goal is to stay alive as long as possible to lock out their revives.

In either case, you probably also want her to be fast-ish. Personally I have her at 265 SPD, but that's because I use her on my CB team. If / when I remove her from that team, I'll probably be targeting around 220 SPD. Since she'll also then mainly be going on my go-second team, I'll also be targeting ~3300DEF, ~50KHP, ~300RES, and ~250ACC.

I have mine built for general content (some PvP, hard DT, dungeons):

240 SPD, 3k DEF, 50k HP, 300 RES, 425 ACC.

Depending on specific stages in hard DT make gear swaps, usually for more RES. 

@kramaswamy.kr Out of curiousity - and apologies if you've said before - what's your CB team?

Currently, Martyr lead, Lydia, Aniri, Brogni, Dark Kael. Aniri extends Lydia's A2, so I get to run a 2:1 comp.

I can one-key void and green, but not consistently enough for my tastes. Really, it would be very consistent, but Dark Kael AI is sadly not great - he uses his A3 even if the boss debuff bar is full. If that were fixed, it'd be an easy one-key UNM.

I'm gonna eventually change to a double ME unkillable team, just because I want it to work on all affinities.

Thanks for the tips both, interesting to see someone using dark kael in clan boss by the way! mine is sitting in my vault as i havent worked out a use for him yet

His damage output is absolutely bonkers in a 2:1 comp. I regularly have him doing 300k+ damage on his A1 (counting the poison explodes, obviously). If you run on full manual, his damage output likely cannot be topped by anyone else. The problem is that on auto, with him wasting the A3 when there aren't enough debuff slots, his damage output drops considerably.

i went as fast as possible so she'd go second on my pvp team, with high accuracy as possible so she'd land her a2 and be my dec def champ. speed/perception sets.  has decent resist as well.

she goes in all my seer comps too so i needed the acc on her a2.

I have struggled with this (got my figures wrong on another thread).  

Currently she is 270 speed, 470 accuracy, 280 resistance, 2.9k defence and 62k hitpoints  which i suspect is not high enough to do much of anything in arena, but she is ok for pve.

If i swap out the banner and boots i can get up to 280 speed, and over 600 accuracy but i have zero resistance. And i was going to use her in a tormin team with the resist aura so go second (3v3).

Seems quite gear intensive to get her right!

The accuracy is way too high IMO. She isn't Serris - her role as a debuffer is important, yes, but her main role is to block revives. If your job for her is to land the DEF down and Weaken, you're better off just running Serris instead.

If you're using her on a go-second team, I think you want her around 400 RES, and maybe like 250 ACC.

I totally understand what you are saying, the very idea of a go second team is being able to survive the first whack ...i just know from experience that even on S4 (tag) i will struggle to debuff anyone with that accuracy.

I agree more res needed, just frustrating being unable to get res and accuracy where i want them