I think her ethical position in that match is also very Marlow - although none of the others would be in a form where marks were more important than matches (possibly Karen). It's not quite comparable to Nick's realisation that you can't dolly (?) out the Head Girl when playing her at cricket, but it is very play up and play the game.

And by contrast, I don't know that her performance is really all that typically Marlow. Yes, in terms of her ability to do it (although Rowan claims to have been terrible as Gabriel), but it's not really an assured competence that I tend to associate with the others. She can do Mary because of her spirituality, and I can see her being an earnestly bad actor in another part. By contrast, her sisters would never achieve the stillness as Mary because they think it's the right thing to keep religion private, but would be probably just as good in any other role.

She's rather brave, I think. It can't be easy in a family where your siblings don't like you very much, and are dismissive of just about every effort you make. But she says and does things because she honestly thinks that they're the right thing, even when met with Nick's full-on revulsion.

That said, I wouldn't be particularly tolerant of her if I had to live with her either.