When I was studying software engineering, we had 10 students with laptops out of the 12 in my year. 1 Sony (that then switched to Apple), myself (Apple), 2 Toshibas, an HP, an alienware, and 4 Dells.
The Sony was sold because it was too big, too slow, the swapbay (where you could remove the optical drive and drop in another battery) basically refused to work and never ejected the optical drive, and was a real pain to work on if the need ever arose
The Alienware was in pretty good shape, but one of the 2 graphics cards in the machine stopped working after 3 months and Alienware took another 2 just to issue a new part.
The power adapter on one of the Toshibas broke, followed by 3 keys and a hinge issue. The other Toshiba was more or less ok for the majority of the time.
3 of the Dells were Latitudes, D800s I believe. 1 of those three was constantly plagued by hinge issues, as well as the wireless cutting out on occasion, it would actually turn off, not just lose signal. The other 2 were fine.
The last dell was an Inspiron that quite quickly started to look and act as though it were 3 years old instead of the 6 months that it was. Fading paint, obvious wear marks, bum hinge, and a flaky trackpad.
My MacBook has been beaten to death, and only now has a few cracks in the plastic after 1.5 years.
My friend's MacBook has a dent in the corner from where it dropped (his backpack broke), but otherwise is working fine last I heard
There were no issues that I had heard about concerning the HP.
I had an alienware that practically fell apart after 2 years of use.
I also acquired a used PowerBook that lasted for 3 years before the DC-In board went bad, after fixing that though, it has been running like a champ.
My sister had an iBook that lasted 4 years or so before the logic board finally bit it (known issue, out of warranty otherwise it would probably still be working)
My buddy's MacBook Pro has had every conceivable issue known to man. The backlight inverter went out, his MagSafe frayed, it runs very, very hot, his optical drive got bricked by an update, and he has numerous dents. Almost all his issues would have been covered by warranty had he actually called. Instead he just dealt with them, thinking that he only had 6 months of warranty.
My other sister had an older Sony that lasted for years and years, she finally replaced it with a macbook because it was too slow and the screen too small (one of those older Sony ultraportables). Also, she has a predilection toward carpal tunnel and preferred the MacBook keyboard.
Another friend of mine goes to a school where laptops are required, and part of the tuition, his Compaq has been replaced 4 times now for a variety of problems.
Finally, my other friend has a Dell Inspiron with a bum DC connector.
The basic end to this is that you can go off of general consensus, that say.... HP has an 80% survivability rating or something, but at the end of the day, it can be luck of the draw. Your girlfriend has had a horrible time with her MacBook, mine has been perfect. Same goes for my friend, his has been running great since day 1.
I personally like the styling of the HPs, and the prices are pretty reasonable for what you get. And from my personal experience, they hold up pretty well.