Why does my girlfriend always immediately complain about everything to do with the gifts I give her?

I know exactly what you are saying. This is a psychological thing so one can only speculate. Here's what i think; i think that your 'lady' is expecting something very specifically in her head and when its something different it completely throws her off because she was already preparing her reactions for what she expected and so when she insults it she is saying everything that is DIFFERENT about it and not exactly what is wrong with it. (tell me if i need to clarify any of that...). Then once shes had the time to really look at the gift she will realize that its a great gift maybe better than what she expected. This is only one possibility however. To prevent the argument you could try giving it to her when she doesn't expect it. under dress the casing of the present. Don't build suspense to the gift and finally, when you give it to her just give her time to think about it and examine it.