How much responsibility do I have to give my GF orgasms?

I'm her first. I gave her good orgasms the first 4 or 5 times I went down on her, but since then her orgasms have been unsatisfying (brief and weak) or not present at all. I suspect there's something psychologically wrong, due to her fears about the future of this relationship. I don't know whether that's the cause of our difficulties. She may also feel broken.

She masturbates occasionally, but doesn't have orgasms by herself--she doesn't know how, and when I suggested she spend some time and try to figure out how, she said she doesn't want to--"It would distract me from my studies." That bothers me, because if she can't get herself off, she can't do much to help me get her off.

What's my responsibility here? Should I just enjoy going down on her, knowing that she probably won't have an orgasm? I could learn to give better head, but putting in that kind of effort would be frustrating, as I really don't believe it would help. Should I be pushing her to explore her body more?

Further fact: She really has no privacy, except when she's at my place.

Edit: I've tried everything I can think of--watching videos about cunnilingus and trying to change my technique, lots of slow foreplay, teasing her and making her wait for me, talking dirty to her. I'm shooting in the dark.