As a white guy who is totally not into "geek culture" at all, I'm in the same boat. And I simply do not care. I'm not going to start playing video games or watching Doctor Who, or whatever, just to fit in.
I'm sure it's infinitely easier for me not to feel like an imposter than it is for a black woman, but of all the real hurdles standing in her way this should be the least concerning of them. Get over it, or the real problems will seem insurmountable.
I doubt its just at work; the silicon valley area itself may be a bad culture fit. From experience, when you don't have people that you relate to face-to-face at home; it gets very depressing. You personally are likely to find people you relate to at home, but they may not.
Being an outsider like that is a huge tradeoff; it can feel like moving to another country.
I'm sure it's infinitely easier for me not to feel like an imposter than it is for a black woman, but of all the real hurdles standing in her way this should be the least concerning of them. Get over it, or the real problems will seem insurmountable.