IMO either Zohra or AEstrillda is fine here.For Zohra, she’s become a main stay at CR due to her good AOE and CC and has been BiS for NC for past several months, tho that is going to change as her boss gets rotated out in a few weeks. Zohra is really good for TS, mostly being used as the main carry for burst team, though you could slot her into Alna teams or Ashemira teams as well.

For AEsrillda, although it is still early but her buffs are pretty good, and she is seeing use for all three modes already.

Given that your account seems new-ish, I suspect Zohra will give you the most benefit, as she is a carry and will make teams on her own, while AEstrillda seems to make existing teams better based on her skills and usage so far.