Is it time to flip?

-Hp is acceptable if you don't intend to run Panic Ploy or Infantry Pulse. Even with a bane it's still high enough to trigger. But if you want to maximize her bulk and force units to trigger an Aether, wait for -Spd. Here's an example of my max merged Nowi I just finished this week. She's +Def -Spd

and this is mine, +def -Hp just like yours with S rank summoner support

As an owner of a +Def-HP Nowi, I would definitely recommend this IV above all others. My Nowi is near invincible and a drop in -4 Spd is actually quite noticeable to how many opponents can suddenly double you. While not necessarily killing you, those extra doubles can drop your health below QR range. Further, the less Max HP Nowi has, the easier to heal up and reach QR range again.