WIP remake of my old Pixel Emma guide from the Marvel Heroes forums. Insignia and Catalyst are not final, nor are Hero Synergies. Also no blessings, pet, or other bonuses not currently available on Tahiti.

For Infinity, start with 6 points into Durability, then 152 points into Attack Speed. Dump extra points into Critical Damage, or take some from Attack Speed and put them here if you find you need the cost reduction from the 100-point bonus. 

Make sure your catalyst has 100 spirit on medkit use to keep your spirit from bottoming out. Use your medkit on cooldown.

For your rotation, begin with Show Off, then Spin Kick to apply bleeding (and vulnerable if you do not yet have Cobra's Hood). Follow with Astral Whip and Inspire Minion, then hit Unlock Potential to buff yourself with Empowered. Use Kneel Before Me now, then repeat the Show-Off->Spin Kick->Astral Whip trio, reapplying Inspire Minion when it runs out. Your goal from here is to keep using Show Off and Astral Whip to lower the cooldown of Kneel Before Me. Diamond Crush is your filler. Remember to manually use Unlock Potential before Kneel Before Me and when both Show Off and Astral Whip are on cooldown!

For your pet, get yourself an AIM Scorcher or Hydra Brawler with Commanding and Frenzied.

Update 1: If you're having spirit issues even with a spirit on medkit use catalyst, you have several options: 

A) Put Infinity Points into Spirit in the Mind tree

B) Drop Cobra's Hood for her personal unique (Locket)

C) Use Rogue's, Punisher's, and/or Loki's Hero Synergy bonuses