I’m thinking of creating a samurai to fight PvM only with the following skills:
120 Bushido
100 Chivalry
100 Focus
100 Macing (to use a tessen)
100 Ninjitsu
100 Parrying
100 Tactics
Would she need Anatomy or Resist?
Why a Tessen? They're really low base damage. The special move Feint halves incoming damage, but with those skills you'd be pretty much un-hittable anyway, Ninjitsu Mirror Images are far superior to damage reduction as they give damage avoidance at 90% when 120 skill. On the rare occurrence something does get through Bushido/Parry will avoid it also.
Unless this is for RP purposes it's a bit of an odd set of skills to combine. You have far too much defence, not enough offense, and unless you were going 4/6 Chivalry or relying on HLL no way to heal/cure, and with a low base damage weapon you won't do enough damage to live. (You'll get wrecked by spells/specials/breath attacks.)
If the goal is to be a Samuari, I would drop Ninjitsu and Focus and pick up Healing and Anatomy, or Resist and Anatomy if you are healing with 4/6 Chivalry. If you wanted to be a Ninja drop Bushido/Parry/Focus and have Healing/Anatomy/Resist with 4/6 casting.
You also want your weapon skill to be 120 before any other skill.