I would expect her to be graceful and maybe a bit diminutive in size. Not necessarily short, but slender.
As for powers, I really don't know. Perhaps sonic. I could also see her being a blade user, dual blades preferably. Dunno if that helps.
"I do what I want." -- Raine Heartfall
Hellgirl. Fifteen minutes could save you fifteen percent or more on car insurance.
@Perfy
Virtue
I would think she is a stalker with some type of blade. With a red costume, Red because of the the Scarlet obviously. I picture her coming up from behind some big enemy and slicing it in the back. I guess it could be a rouge scrapper with invisibility, oh wait that would be a stalker.
I would LOVE to have her with a whip..but you know..City of heroes just isn't that cool *glares*...alright it's pretty damn cool. but still...a whip would be bad ***...PSU has a whip..can't CoH have a whip? *pouts*
Maybe like an energy blaster with wings, then tint the energy powers red.
Heroes : Angrem (50 Stone tank), Exo Inferis (50 Fire blaster), Exo Proteus (50 ill/emp), IceVengance (50 cold defender)
Villains : AtomBomb (50 Rad/Kin corruptor), Aleks (50 SS/Inv brute), StoneLethal (50 EM/Stone brute), Davroz (50 Bots/Dark mastermind)
I don't know Limedolly. Scarlet Finch makes me think of..... *dreams*
<ANNOUNCER VOICE>
...in the 1960's one man's battle versus the forces of intolerance...
Atticus Finch: "Don't give up hope Tom! We'll win it on appeal!"
...didn't turn out like he'd plan.
Atticus Finch: "There won't be an appeal. Not now. Tom is dead!"
The forces of intolerance are on the rise again and he's needed once again but THIS time, it will be different.
*RIFLE SHOT*
Sherriff Tate: "Didn't you know your daddy was the best shot in the county?"
In a world gone mad, one man stands up and smacks it around until it gets ahold of itself. That man is ... The Scarlet Finch!
To Kill a Mockingbird 2!
Die Mockingbird Die!
Let us stifle under mud at the pond's edge
and affirm that it is fitting
and delicious to lose everything. ~ Donald Hall
Scarlet Finch sounds like a swashbuckler to me. Try Dual Blades/SR or Broadsword/SR.
<QR>
Sonic/Mental blaster
Well - if you have a literalist streak in you....
Finches are songbirds - so maybe a sonic/(something colored red) secondary. Or perhaps a plant/sonic controller. (They like seeds.)
What immediately jumped to mind was archery/fire blaster. Which isn't to say that's a sterling combination but that's what I thought.
Perhaps edit it to Energy/Fire with Energy tinted red as others suggested. Since finches are little birds, I see her (sorry, I can't see it as a male) as a blaster/defender -- staying out of the way of melee. Also, I don't "feel" sonic for her. Finches cheep, they don't make powerful cries 
Like Rookery I keep seeing To Kill a Mockingbird.
Maybe a superhero Scout Finch? Sonic blaster would probably be a good choice.
Alright so I've been holding onto this name 'Scarlet Finch' I have a background story roughly set out in my head and even a basic costume to start on, only problem I'm having is powers.
If you came across a female superhero with the name 'The Scarlet Finch' What powers or abilities would you expect her to have?