I think the question is in the same territory as:
"oh, you're from overseas, have you considered what it might be like to practice as a foreign MD coming to USA? have you shadowed foreign MDs before?"
"oh, you're 'insert minority', have you considered what it might be like to practice as an 'insert minority' MD? have you shadowed an MD from your race before?"
"oh you worked X job, have you considered what it might be like to practice coming from Y background? have you shadowed an MD with Z lifestory before?"
I think it's fair. The interviewer wants to hear your opinion and is looking to see how you will respond.
They could ask the same question to male applicants also...
"With all of the arrogant male MDs (insert random statistic against insensitive male doctors here), and a need for female primary care physicians, why should we admit another macho guy like you into our brand of MD program? have you considered shadowing a female MD before? how will you handle motherhood?"
I've been asked some awful things at interviews for jobs, etc, but I think it's fair that they should put you into an uncomfortable position. Just think of the ridiculous offensive crud you will hear during your future as an MD. As a female, you may even get sexually assaulted by an aggressive patient or followed home etc. You will also have to make sacrifices for your family by working long hours and will likely have to delay forming a family until you are well into your 30s. Now, before you sign away the next 10 years of your life and make these sacrifices, do you still think that it is offensive for an adcom to ask what your true intentions are?
The PhD comes off as rude, but may be she regrets her own decision to pursue a PhD because of the sacrifices that she had to make. May be this is why she is bitter. She is asking you the same question she would have asked herself if she were to interview her younger self, in a profession historically dominated by males and because of the traditional family structure.
Also, how is it fair to the community if you end up working like 20-30 hours/week in a saturated specialty for work-life balance, specifically because you want to be a mother with 10 kids? Whereas others may be willing to work like 50-60 hours doing grave yard shifts, serving to the north of nowhere and fully devoted to this profession.
Look, I was born in a country where several MDs get attacked and killed by angry patients/families every year ... The financial returns are also nowhere near what you get in the US. Yet I would do this profession even if I had to serve in a war with blood and guts spiling to the left and right of me, and even if I lived in Sub-Saharan Africa where a significant percentage of the population has HIV/AIDS.
Medicine is not rosy. Expect some awful situations down the road and your feelings will certainly get hurt by more inappropriate events.
You have to be prepared to tough it out. Clearly, there are better ways to live your life if you want work-life balance and to have a large family. You don't need an MD with six-digit debt to do that. The only reason I say this, is because I know several women who went to medical school to become specialists, only to give up their career in their late 20s/early 30s after having 2-3 kids (and marrying other specialist MDs). I should also mention that their educations were subsidized by the state. How is that fair to the state when it invests so much into you and you leaving?
Others may disagree, but it is what it is. Not everything is PC.
