I started working over a decade ago, at that point hijab was not an issue at all.
I think it depends completely on her, if she wants to go for a job and then put her hijab on when she starts that is going to land her with a whole heap of issues as well, if they really are against her wearing hijab they can still get rid of her within the trial period of her job or make life utterly hellish.
I have always been a great believer in starting as you mean to go on.
Does she want a job in an environment where she will be stigmatised for her religious beliefs?
I'd start asking for more detailed reasons as to why she didn't pass the interivew stage, I'd also look for jobs that aren't specifically grad jobs, I didn't bother when I started just got a position as an assistant and the training and promotions came to me themselves alhumdulillah, you need a lot of common sense and be very articulate and able to explain things in lay terms (well in my position you do).
Also from a religious point of view, if something passes you by it was never meant to be for you, whatever has been written for one will be given to us we merely choose the road to get to that destination, I always prefer giving up something for the love of Allah and when I have done, it has been returned to me a thousand fold in the most beautiful and unexpected way.
I regularly recite surah waqia at night for rizq and surah mulk when searching for a job.
It's up to her how she wants to go about it, but I think it will be far more difficult for her to begin wearing a scarf if she starts without it. Does she want to work in an environment that is hostile for a muslim woman to be in?
I suggest she do istikhara and seek guidance.