I'm not a great fan of hers, but I don't think she could be accused of racism, and by the way, it is historically true ! Politicians would be well advised to not twitter, it gets so many get of them into hot water.
Her comment seems fine to me in the context of Imperialism/Colonialism, it was a handy skill for the Empire! I think people are being a little over-sensitive.
Rather a naive comment by her perhaps but not racist. Lots of people make ill-advised, sweeping statements about "white people" and "black people". As someone else has commented there is a bit of historic background to this which may or may not be appropriate today.
And as I said elsewhwhere, Twitter is like an online toilet, and it is a fact of life that people cr*p in toilets. One day we'll get over the novelty of it.