If her Amazon already has high pierce, like in the range of 70-80%, then you could very well stick to the Nosferatu's Coil. Pierce is excellent for bowazons, but in my mind it's most critical for Frostmaidens or Frozen Arrow and Lightning Fury builds, where much or most of the power comes from special effects like cold damage explosions or extra bolts released with more piercings. In these cases, 85%+ pierce is excellent and 100% should be the ideal.
Nosferatu's Coil also has 10% slow on it, and combined with the knockback from Windforce, should keep her bowazon very safe. Slow and knockback offer extra crowd control, and that could be worth a slight loss in power that would be gained from adding Razortail. With a WF, she should not be lacking power. You could also put a +15 max damage jewel or two in a unique or socketed armor to make up for potentially lost damage.
Nosferatu's Coil also has 10% slow on it, and combined with the knockback from Windforce, should keep her bowazon very safe. Slow and knockback offer extra crowd control, and that could be worth a slight loss in power that would be gained from adding Razortail. With a WF, she should not be lacking power. You could also put a +15 max damage jewel or two in a unique or socketed armor to make up for potentially lost damage.