My group is playing a game based in New Orleans, and I set up the adventure to center around a mysterious string of drownings. The cause is a group of river fae, beautiful female creatures that appear unexpectedly, then summon water to them and lash at those nearby in fear and anger. I am imagining them as "spirits of the Mississippi river" (though spirits is kind of a loaded term in the Dresdenverse, so I'm using the Fae templates.)

Designing the creatures and how their magic works has been more of a challenge than I expected, however, and I could use some tips to get these deadly ladies up and running.

I want to use them several time throughout this story, but I imagine the first scene where I use one like this. The party is investigating a property where 15 people were found dead, apparently drowned in a dry room a mile from standing water. Suddenly a scantily clad beautiful dripping wet young thing flops out of a portal in the middle of the room. She looks around in a panic, gasping as if the room lacked air, then as her eyes focus on the party her face fills with rage. All the windows and doors in the building suddenly fly open and water rushes in through them, starting to fill the room.

Here's what I'm looking at so far:

River Fae
High Concept: Embodiment of the Mississippi
Skills:
Discipline: Superb (+5)
Conviction: Great (+4)
Athletics: Great (+4)
Deceit: Good (+3)
Stealth: Good (+3)
Alertness: Fair (+2)
Fists: Fair (+2)

Stunts:
At Home in the Water (Athletics:) +2 when using Athletics while Swimming

Powers:
Aquatic [-1]
Glamours [-2]
Incite Emotion (Lasting Emotion, at Range) [-3]
Inhuman Strength [-2]
Inhuman Recover [-2]
Inhuman Toughness [-2]
Channeling (water) [-2]
   Refinement (water) [-2]
The Catch [+2] is cold iron and the like, and being out of water.

The water channeling thing in particular is giving me issues, as what I want these water creatures to do doesn't really fall perfectly into the channeling motif (and I'm pretty sure I'm breaking some rule by picking Water Refinement twice without getting a bonus in something else first, but it's not like Channelers CAN choose something else so that seems to be a catch 22.)

Here is the big spell I was thinking she would use water channeling for.
Summon Water
Power 10 (3 for maneuver on zone, 3 for maneuver on people in zone, 2 to widen to zone, 2 for duration)
Opposed by: Athletics or Endurance
Effect: Maneuver places a "Flooded" aspect on the zone. Also, people in zone are attacked (+3) vs. Athletics and those who fail get the "Floundering" aspect.
Notes: Repeating the spell in subsequent rounds makes the zone aquatic and stacks the duration. People in the zone are attacked (+3) vs. Athletics (or Endurance) for 1 stress instead of getting the "Floundering" aspect.

I was thinking this would kind of be like a mass Orbius spell, with a bit of area manipulation thrown in. The river creature would spend two or three rounds summon up water (either from a local source, or creating it from ectoplasm from the Nevernever) and then start unleashing more conventional water whip or whirlpool attacks (which are not the ones giving me a design headache.)

The party is at the Chest Deep level. There are four or five of them. I would like it to be a close call when they encounter one of these ladies for the first time. I could really use the help of a rules lawyer or someone with an eye for balance for this.