Aura Choices
Pistol Amp - Just basic secondary damage boost, usable until you can switch to Growing Power to get occasional burst of boost to ability strength for Merulina HP
Growing Power - 30% Ability Strength when your weapons cause a Status Proc (You will be highly likely causing procs with most Secondary Weapons paired with Yareli i.e: Pistols that use Cascadia Flare)

Exilus Slot
Power Drift - Additional Power Strength
Speed Drift - More Cast Speed (Faster Sea Snare) & Sprint Speed (Useful now since we're not on Pseudo K-Drive)

Mods:

Primed Sure Footed - used because Loyal Merulina doesn't grant Knockdown immunity.
Alternatives - If you can deal with occasional knockdown you can swap to these mods:
Amar's Hatred - Slight Ability Strength and Mini Kullervo's Heavy Attack Teleport
Armored Agility - Small Movement Speed Boost

[Archon Flow] is used for the chance of dropping Energy Orbs on kills done with Riptide as well as hitting the 700 Energy Threshold needed for [Angstrum] & [Atomos] Incarnon's Paladin Virtue Evolution II Node for bonus Critical Chance. If you are not scaling the chance for energy orbs and just want to fulfill the Energy Threshold Primed Flow will also work for less Mod Capacity drain.

Energy Nexus - Passive Energy Regen for Yareli. Simple As.

Blind Rage - You'll have enough energy to go around as after casting Merulina it'll be mainly for using Sea Snares occasionaly to crowd control or Riptide for grouping enemies together.

Transient Fortitude - Most of her abilities have long enough duration you can swap Continuity out for extra Health for Merulina & damage for Aquablades & Riptide

Augur Secrets - Lets you get Overshields Status if you don't have it activated yet.

Subsume Alternatives:
Preferrably subsumed over Sea Snares (Don't need CC) or Riptide (Less reliable Enemy Grouping)

Roar - Ol' Reliable Damage Boost

Airburst - Can use Airburst Rounds Augment to also increase Secondary Damage (Might need to swap PSF out for Armored Agility/Amar's Hatred & removing Augur Secrets off.

Empower - 50% Additional Strength to further [Juice] up Merulina HP