I don't think you cleared the level 2 dungeon in this save, since there are still lots of opponents around. Anyway, I assume when you had to replaced your inventory files there is something in them not lining up with the BF dungeon containers. If you used files from a new save, they might not have entries for BF containers (the BF dungeons are randomly generated when you first enter the BF each act).
The only thing I can think of that might fix it would be to drop all your stuff and save, then replace the inventory with a set from a save just after reaching the BF (you can get the first BF key pretty quick in a new game, especially if you boost your stats and hex teleport directly to the arena). After loading that save you could pick up your loot (the game may remove some of the equipment when you mouse over it), then enter and exit the BF a few times to buy replacements for anything removed or corrupt.
Since you are at the end of the act, it might just be easier to skip the second dungeon and check out the third. There are 6 dungeons each BF in later acts, so skipping 1 or 2 from the first act will not make a big difference (I only ever used the BFs for the traders).
I'll rephrase part of what I said about the inventory file sets (I did switch over, as an example);
My inventory files from an act 1 save keep your save from crashing in the level 2 dungeon. However, they also result in most equipment being corrupt. If you try my act 2 inventory files in your girlfriend's act 2 save, the same thing may happen.
Also, I don't recall if I had been to the BF yet in that save. If that is what is causing your BF crashing, then that would be another possible complication trying to fix your girlfriend's inventory.
