Using nightsister zombie properly

It depends on what you want to use her for. My experience is that she needs G12 for HSith and GA.

Can get 5 mill in HSTR with a G11 zombie.
You'd want g12 for better score or for use in arena, ga, tw

For hSTR p4 a g8 zombie with health primaries will suffice. As soon as you get her to +50% or even +100% speed, she works well and you can score more than 6 million.
For hSTR p3, the more gear/health the better. Even g11 can seem a bit low. (paper Talzin and Initiate make setting up a goid run easier).
For arena, the more gear the better.

It's definitely worth pushing zombie to g12. Because the 2 proxy deaths NS now get cause zombie to lose all protection, usually long before its lost from damage, she benefits far more from really high health and armor than from protection. At g12, zombie has both a medpack and furnace available, adding over 12k base health, and also allows the use of 6e health mods. With both g12 pieces and a couple 6* mods, you can boost her max health to 50k+, which will drastically improve her ability to survive multiple hits each revive. This is essential to keep those -50% speed stacks off of her which turn her into a glorified statue.
Her max health also affects the new part of her kit that heals other NS allies, and under AV lead this extra healing will let them heal back to 100% health more often to get the 50% bonus TM when they next drop below 100% health.

Better to have her g12 and fast.

I think in any case zombie need to be very tanky for fulfilling her needs ( constantly taunting and being a pain). And as i see it (run NS in arena now) a slow but alive zombie is way better than a fast one with -100% spd.

Get her G12, mod for health ( trangle, cross, , circle), crit avoidance on arrow, health secondaries( moderate speed secondaries will be more than enough).

I think i doubled hSith score and got more consistency in fighting revans after remodding her like that.

PS. Don’t worry about speed, once you keep two stacks of speed you will be more than good