Did I behave badly or there is some over reacting?

Hello, first time posting and i really need someone to speak to.

I have to premise a fact. A couple days ago, suffering heat, my gf said that she really would have liked ice creams but pleaded me not to purchase those as having those meant she would have eaten them and she preferred not. Stupidly the next day I actually purchase them as I wanted her happy, but in the end I did not listen to her wish.

Today's my GF birthday and yesterday she planned to wait for midnight with a group of friends. 
Snacks were to be had, and given the intense heat and tiredness I offered to go buy things in her place.

We wrote a list of stuff to buy, and she asked me not to buy 'classic' chips, the normal ones, then I went to the supermarket. Upon purchasing stuff I decided to buy, in addition to all the stuff she said to buy, classic chips: my idea was that she would not be eating those and maybe the other guests could find those enjoyable and, thus, be happier.

Having something more is in my mind better than have something less, and I was paying for those, so I went for it even if she said no - I just thought she didn't want those for her, not that it was prohibited.

I then buy a small stock of bottled ice tea (no sugar) as we drink it with the intense heat around here as a refreshing drink, bring everything home ready to go out again and grab beers in a different supermarket.

She is baffled when she sees the first things I bought, noting that she didn't want those chips and that it was stupid to buy that much iced tea instead of the beers. I go out to the next supermarket instead of arguing, and I do the next mistake. Instead of buying a beer for each participant I buy some bottles in a good enough - in my opinion - amount. 

Once I get home *** unleashes. It appears that I really should NOT have bought those chips and that i should have bought a beer each, that I don't care about what she says once again, that I don't listen to her, that I am an ***, that I am dumb and a crazy madman and a fattie since I bought a lot of tea instead of the required beers and I had to do two trips for this and that she would prefer throwing all the unwanted stuff away more than having it at home. These are mostly her words precisely, i am not exagerating stuff. She also states that the beers were not enough and i should have bought one each (in the end i was right, and we had to bring home the beers we brought in addition to the ones I bought).

At this point I am quite upset, but I always try really hard not to scream or overreact while she screams at me, and not to state how i feel as things would get worse.

I say that I will go buy the missing beers, and while I dress she slams the chips on my chest and says "and throw these away!". Hugely upset about the physical interaction, that was 'violent' not in the harm (there was none) but in how it was done, I pack the unwanted chips and tea and throw those away in the garbage bin outside just as she told.

Probably not the brightest idea, but I guess I have a boiling point too (fortunately the stuff was later on taken by some poor soul, as when I went back to the bin to take it back it was no longer there but other trash was).

This sparks a whole other situation, as now I am crazy and stupid and a madman as I followed her instructions and threw the stuff away, and the idea of having thrown stuff away makes her sad and angry and it's obviously my fault.

I am told that I completely ruined her birthday, that she wouldn't go waiting midnight with her friends, that she'd stay at home and that I am an *** and all other stuff like this. She says that the next day(her birthday) she wouldn't want to spend time with me at all and that I would not be invited to party at her parents' place, and that I should not dare to wish her happy birthday at midnight.

She then after a while decides that we should go to the party, it goes on and I hope she enjoyed it, I was there but tried to not be too present, and we get back home, angry with each other.

Now it's her birthday and I am TRULY upset. 

I feel like I have been treated really harshly, I have been said a lot of terrible things, and all of this because i decided to buy - in addition to all the other things - stuff that she did not want.

So i ask you, given this wall of text that i feel a bit ashamed of having written (i mean, from my point of view this is all about chipset, and i feel stupid writing about this), am i really that much of a bad bf? I can see why she feels not listened to, but i can't stop thinking that things have to be looked at from reality and not in an absolute sense and while I did not listen to her what i did was simply buy two things in addition to everything else.