Hi!
I think Phyla-Vell have a good potential in PvP. If you are planning to pair her with a Guardian Galaxy Rocket Racoon its a good choice since his passive give attacks Guaranteed Critical and she have 3 of 4 skill with Deadly Crits that said we need to imagine her with lvl 15 with Scrapper bonus and Rocket following her, as well Summer sale gift Rapier could combo too. Another GoG is Drax since he give Hemorrage os his passive but I dont know how to use him and his Herioc battle proved it. I dont think Gamorra pairing with her its a good idea because they do almost the same thing with their skills so I dont feel they are compatible. But you can try Agent with Guardian Insignia to activate passives (Survival Training to Phyla) and another hero to go as support or attacker, for eg: Mantis or even Moondragon for psychic protection (both Mantis and Moon are GoG too). Also she is both Bruiser and Scrapper so Molly isnt a bad option with her passives (immune to Fear and Stun) and some new E-Isos for Bruisers.
Speaking on E-Isos she can equip Scrapper only iso so PvP 22 reward or Insult to Injury seems to be a good choice, preventing Lock Out effects (at least melee L 1 and 2). Close Emp E-Iso could help to increase Critical Chance If she is not paired with Rocket. And as for A-Iso I think on Vorpal, Hemorrhaging or Vampiric on her L 1 and L2. L 6 I dont recommend to use anything since its Quick Action. And for L 9 Supression (shield maybe?) or Ionizing Im not sure.
The main problem is the new meta Faiza but Mangle could finish this problem (I need to test).
I hope I could help or ate least give a direction to you to think about a strategy.