Oohh, good question!
My girl will definately have to wear the brave face, she is lacking in almost every quality she thinks a leader should have.
She will make leadership decisions reluctantly if she has to but if there is advice given by someone who she sees as more worldly or experienced than her (mostly everyone lol), I think she will definately take that advice over her own plans or ideas.
Most of the time she will stay pretty grim and straight-faced in front of the others, she lacks confidence in many aspects of her life and I don't see her being able to pretend otherwise, she will look for confirmation that she has done something right or good.
She scribbles thoughts onto paper, so I imagine there will be many mini novels written as she gets the panic of battles & situations out of her head and onto paper, that has been her therapy for dealing with stressful things throughout her life, I see her continuing with that, certainly in the shorter term.
She is funny but she won't recognise that in herself to begin with so any attempts at humouring a situation would be few and far between and either be badly timed, almost cringeworthy or just fall flat. I can imagine many eye-rolls from her companions.
My hope is, as she builds bonds with the companions/advisors, I see Cullen & Varric being very good for her, if they believe in her, she hopefully will start to believe in herself, becoming quite confident and assertive.
I think she will be a strong leader as the game progresses, although her heart may rule her head more than it should.
Varric will be a bad influence on her and introduce her to a wee drink after battle, for good or ill lol.