Girlfriend is impossible to deal with!

I've been with my girlfriend over 2 years now. We've lived together for just over a year. Recently, she's become impossible to deal with, culminating in her today telling me that I've made her feel worthless, the reasons being that I don't compliment her or pay her enough attention. I used to compliment her, but she'd laugh, disagree and call me 'happy' (you know what I mean). I try and talk to her but she looks at me as though she wishes I'd shut up because I'm boring. I'm into science, engineering etc and sometimes talk to her about my studies, my day at Uni, what went on. If it doesn't involve celebrities/TV programs/someone's personal life, then she doesn't bother replying. She gets plenty of attention; I'm always tickling her neck, stroking her hair etc, all things she likes. She wants to go out more together, except she doesn't like eating in public, doesn't pick anything to watch at the cinema(then refuses anything I suggest, which is often the entire list of films), won't even go for a walk anywhere.

Also, everything I say is apparently criticizing her. She's never been taught to cook, I tell her to shake the pan as we're frying eggs, she says she wants to learn from her own mistakes and that I should stop judging/criticizing her. I'm trying to help! Same thing can be used in any situation.

Today I was revising for an exam tomorrow. She comes up and says she wants to sit on my knee, I say no I'm busy, she says "yes", I just say no, then she says "come on, just 2 minutes". I again so now, I'm very busy. She storms off claiming that I never pay her any attention. My exam tomorrow is the final exam for my module, I have to revise. 2 minutes always turns into an hour of laying in bed together. I'd already asked her not to interrupt me too much today when she decided to tidy up, rattling bin bags in front of me.

I just don't know what to do anymore. I love her but this has to stop. In my opinion it stems from her parents (they were supposed to be coming to see our new flat; we've lived here for 3 months, but they canceled, as usual). They've never made her feel valued, preferring her sister over her, and never make any effort with my girlfriend. When we moved up here (130 miles from them), they didn't even get out of bed to say goodbye. She's criticizing me all the time (latest being I can't be relied on for anything because I forgot to buy sellotape), despite the fact I drop everything for her when she needs me. I feel like she takes everything out on me instead of saying what she thinks to other people.

For the record we're 21, she's just finished her degree and we've moved up here because she wanted to get away from her family/friends and start a new life.
Girlfriend is impossible to deal with!
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