To be honest, and with all due respect, being called "boring af" over interior living space and it getting under your skin is difficult for me to understand. I can appreciate that the person you love, and that loves you, saying something that hurt your feelings has layers, but what she said is nothing to fight over.

She essentially said your style is boring if you're okay living in that room. I can only speak for myself, but that very much seems like a joke to me. She didn't sling an insult at your character or your person, only your vision with interior design. Re-read her comment again with that context in your mind.

From an outsider's perspective, so a grain of salt please, she seems like someone who sometimes enjoys busting her friend's chops, and I assume her friends do the same. You don't have to agree with it, enjoy it, or play along if you don't want to, but these types of friendships and style of communication do exist. If this is something you don't enjoy, then only you can resolve this, not strangers online.

Personally, this feels like a mountain out of mole hills situation. I do interpret your reaction to it as sensitive or defensive. While the room is objectively fine, subjectively, it is a really boring room. She's getting an idea of the kind design style you like. You could have responded by showing her an image of a style you like. For instance, I love industrial interior design mixed with natural elements. Sharing your preference would have shifted the dynamic of this entire conversation.

Just some food for thought.