Would you get mad if? (to the ladies)?

Ok, so I had this idea for months now. I was going to buy my girlfriend and I some purity rings to signify our pledge to stay pure for one another. I am a big mouth though and leaked to my girlfriend that I was buying us rings like she had always wanted. She then gets enraged because she did not have the chance to pick them out, even though they were my gift to her. Should she be angry at me for trying to do something to make her happy? Will she want to pick out her own engagement ring in the future? That is not how its supossed to go right? The male should express his love for his girlfriend right? Did I do anything wrong besides telling her before the rings came?