How is my nowi coming along?

You should invest more in SI. You need Fury 3 on her A slot on her B slot Wrath / Guard / Vantage 3, her sacred seal should be QR 3 and her special should be Bonfire / Aether. Other than that she is ready to go.

That's wonderful def on her for sure to not let Falchions kill her, but I agree with the other person to SI her further and she seems to have a -atk bane. A dragon's favourite A skill is either Steady/Warding Breath if you have one of those to spare, Fury 3 or Atk/def 2, Atk/res 2 would be more budget options. QR 2 is good enough as the budget option but I recommend QR 3 for the extra arena points once you +10 her. Aether really helps by giving a form of sustain to her and works really well if you have Steady/Warding Breath, otherwise Ignis or Bonfire works. Hopefully you get enough sacred coins soon to upgrade that DD 2 to 3. Her C skill can stay the same, or changed to suit your team.

Here's my precious +res -hp Nowi that I use in both arena offense and defense.