Here in the states that would not be considered "discrimination." She's not targeting a specific class of people (for instance she can't say "white people only," or "gay people only," "no disabled people," etc. )
I can't see why she wouldn't be able to say, open to writers and artists. It might cut down on her revenue, but it's not discriminatory. Curious what Airbnb has to say about this.
I think the unique thing about Airbnb is that we aren't supposed to be hotel equivalents. Eclectic is a selling point.
Maybe it's a marketing opportunity for Airbnb. A category that says "perfect for writers and artists," etc.