Everyone saying you don’t have copyright or patent on interior design choices & that we all copy from somewhere are missing the point.
Why this feels the way it does is because you showed your friend something that you were claiming as yours (meant in the loosest way of course you don’t own the right to it literally) & she went & took it from you.
Everyone’s had a friend growing up or sibling who used to do this - it’s about territory more than anything. By showing her your choices - you’d claimed that “territory” as yours & she liked the look of it & the kudos it would give her because she clearly lacks style, confidence or taste or originality & decided she would have it for herself.
I think it’s deeper than flattery. I think it’s about deception & competitiveness. She deliberately decorated & furnished it before you had a chance & beat you to it. Then showed you the finished result!
I’d find it highly irritating - it’s a boundary thing & she’s not respected that.
I call these types magpies - they see shiny nice things & want them for themselves & don’t care what it means for them to have them.
Of course we’re all influenced by fashion & each other but the context is all important. OP didn’t invite her friend to get the same or give her approval to go for the same look.
Some people just don’t get these nuances however or seem to understand that an expression of your taste, or identity can be important to people & that by stealing it & claiming it as your own, it feels uncomfortable & weird. They however seem immune to this & act either deliberately ignorant of their actions, claiming it to be theirs from the start, or perversely act slightly triumphant when they show you your design, already fleshed out & in situ in their own home.
Territory, power dynamics, insecurities, envy, belonging, identity, aesthetics, home, fashion, sibling rivalry, friendship, boundaries.
All over sone lamps & a tin of paint! Who knew?!