Ring Drama!!!

Sooo I'm in an odd situation.. My brother and his teenage girlfriend live with my SO and I. We have been together for a few years and have a daughter together. We're not the most financially stable family But we make it work with lots of love, happiness and sacrifices. I recently picked out a certain ring&bracelete from a certain store that I absolutely Love!! We couldn't afford it in the past, but my SO is buying it for me within the next week or so. It really means alot to me..My brothers girlfriend that I just so happen to share EVERYTHING with, is now having my brother get her a similar set from the same store. She has the nerve to ask me for the info and location so she can have him get it for her... I got beyond annoyed!! I feel almost childish for calling her a copycat.. but in all reality she is!! The same boots, clothes, hair style/hair color now this! I just got fed up. She ended up saying fine she just wont get it, but I could tell I hurt her feelings.. My mom said look at it like she likes my style and wants to be like me and doesn't have a sister to mimic and look up to so on and so on... My thing is it's rather frustrating that he always tries to have an "One Up" on me when he gets her similar things, while she uses and wears all of My stuff. My questions is am I wrong??? should I just embrace her envy and basically approve her wanting/getting the same set as me?? Or would any of you ladies have reacted the same as me???