Threads like this always make me wonder if most MNers have massive chips on their shoulder. It's ludicrous to think that the decision she is making is symptomatic of what other women have to deal with. It does not mark a step backwards for working women, no a lowering of the glass ceiling.
Of course she can't balance the needs of her family. Her family is highly abnormal - with her husband living in New York. It has nothing to do with her being a working woman, an MP, or anything else. The Tory party (and I'm no fan) seem to have done lots to try and help her balance things, but there's absolutely no way that they could or should be doing more so as she can manage life more easily when he husband is in the States. That would be ludicrous.
And as for the 'well he should give up his job' line, don't be so presumptuous. She's hardly a put upon wifey. I would bet my bottom dollar that it was roundly debated in the household and I'm reasonably confident that his superior earnings will have been a deciding factor. That's a sensible decision in any family (where the decision is about MOVING continents, not about giving up work, remember). And unless you're thinking that MPs should be earning the millions he probably makes then it's hardly surprising that the decision fell the way it did.
FWIW I have spent the last decade working in the oil industry - which is about as male dominated as it comes. I have never encountered an ounce of sexism and I know lots of incredibly successful women (mothers and not) who have worked their way through. However, like every other working mother I know I do sometimes have to make hard decisions and sacrifice time I'd like to spend with my family. But that's just life. And my husband makes similar decisions every day - in fact he moved jobs after our first child was born (which involved a significant pay cut) so that he could be home more than he would otherwise have been. Both women AND men make these sorts of decisions all the blimming time.