I'm assuming this is a legit inquiry and you're not trolling. FWIW, I'm in my thirties and have been with my partner for 10 years. He's in his forties.
First of all, why do you feel a need to get married at all? You said you are finishing a graduate degree and on a nation-wide job search, she's a "high-earner." Seriously, if there aren't the financial pressures many couples face--it's possible it would be more advantageous for you two to file separate tax returns anyway, if you're both really high earners--what's the rush? My partner and I aren't married and we're very much in love and happily living together. We have been together through graduate degrees and moved for jobs, and so far, it's worked. Yes, it stinks to sometimes get judged about our decision by older generations or nosy a-hole, but on the other hand, it is a little fun to give a response that makes people squirm a little bit. If one of you REALLY needs to be married just for the sake of being married, and the other doesn't, that seems like a problem.
Second, I agree with what others are saying about compatibility and shared interests. You don't have to agree on everything or have exactly the same taste in movies, restaurants, hobbies, etc. -- but it certainly helps to have SOME activities that you enjoy doing together. More important than that, though, is conversation and communication. Some questions to think about: Can you be your true self with her, or do you feel like you have to morph into some alter ego? If your friends saw a film of the way you are around her for, say, a full weekend, would they recognize you? When something monumental happens in your life, whether it's exciting and happy or devastatingly sad, is she the first person you want to talk to about it? Can you talk about the fact that you don't share a lot of interests but still care for her without fear that THAT conversation alone will end the relationship? Do you bring out each other's best qualities? Have you argued or fought in a way that actually resolved (or worked toward resolving) the underlying problem, or do you fight and never bring it up again? Or do you never fight? Has one (or both) of you experienced something horrible during the 4 years you've been together? If so, was the other person a good support during that time? My partner is my best friend. I saw that some other commenters have said the same thing. It sounds trite, but it's a pretty good metric of happiness in a relationship, I think.
Third, it sounds like you feel some pressure from your parents to be with someone who has the same ethnic background, but please, don't marry someone just to placate your parents, whatever the reason. Your parents don't have to share their life with this person, you do. If sharing the same ancestry is important to YOU, it might be different, but since you don't care about that, it shouldn't be a priority. I will add that I am a child of a bi-racial relationship and am in one myself. I don't think that I'd be any happier if my partner were the same "race combo" as me.
Finally, as others have said, the fact that you are asking this question indicates that marrying this person--at least right now--is not a good idea. If you are looking for reasons or justifications to either end the relationship or not pursue marriage, I think you have plenty.