hi boona i think you are being a big over sensitive but i can totally understand where you are coming from. my sil is a pain in the back side she copied everything i want or do. i decide my boys need new shoes, so do her girls, i want to paint my living room so does she. i also wanted to call my second child kaylee if it was a girl, and she knew this and chose kaylee for her daughter. luckily mine was a boy but i was really anoyed too.
when i get wound up my partner says, sje obviously has no imagination of her own if she has to copy other people, and he is right.
try not to let it bother you, although easier said than done.
good luck with everything x