Who did I mistake her for?

Having just seen her in About Time, I tried thinking a little harder, and came up with maybe Summer Glau? When they're both wearing their hair swept back in the middle there's some resemblance...still feel like I'm missing someone even closer though...

agree on summer glau in some pics...but also compare a few pics of her with a few of mary elizabeth winstead....

I decided she looked like Clara (Anne Bonny) Paget in Black Sails. Paget has a more exotic look out of her Anne Bonny costume, but in it with her hair hiding her cheekbones and slouched hat hiding her eyebrows I think there is a strong resemblance.

Hey, I know it's been a long time and you probably won't even see it, but I came here for the same question.
She has the same doll beauty of Clara Oswald, the Impossible Girl from Doctor Who series, portrayed by http://www.imdb.com/name/nm1982510 Jenna Coleman, but she's even lovelier.

Hm, could be, I did watch Doctor Who until recently. But, I think she was already a regular at the time I posted this comment, so I probably wouldn't have been so confused...still gotta go with Summer Glau as my best bet :) Jenna Coleman has a very open face while Lydia has some finer features that make her look a little more reserved, so I see the resemblance but I don't think that would've been it. Thanks for suggestion though!

Hannah Tointon ?

Hm, I haven't seen any of her work so probably not. Definitely see the resemblance though! Thanks.

I just watched her in The Making of a Lady and felt that she bore a striking resemblance to a young Gwyneth Paltrow, in that particular film at least.