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It would seem the key problem here is immaturity (both the LW's BF & poor Alex). I know that when I was 18 or 19 and found out that a girlfriend was much more experienced sexually than I was, I was flooded with emotions that I couldn't understand. Trying to organize those emotions, I put them in the convenient box lying next to me labeled "social norms" and thought she was an irredeemable slut. Luckily this woman (and Alex, honestly, what grad student actually calls grown women "girls" anymore?) pointed out the complete baselessness and knee-jerk hypocrisy of my view. I've never made the mistake again.
Finally, a word for benighted Alex, no one is impressed with your being a grad student. Having once been a grad student and now being a professor who trains grad students, I can attest that there are a tremendous number of grad students (and professors, doctors, professionals as well) who complete fucking morons. We credentialize ourselves with our ideas, not our affiliations or a bibliography.
So, the BF & Alex have to grow up. Maybe they will, maybe they won't. There seem to be plenty of people in this world who never manage.