Buying for a koala-loving her comes down to one question: does she wear her fandom, display it, or live with it? Answer that and the gift picks itself.
If she wears it
Jewelry is the move — a delicate koala necklace or a pair of stud earrings is subtle enough for every day and sentimental enough to matter. Apparel works too if her style leans casual: a soft hoodie or a pair of novelty socks.
If she displays it
A piece of wall art or a tasteful home decor accent lets her fold koalas into her space. Watercolor prints and minimalist line drawings tend to read as "decor" rather than "merch," which matters for a grown-up aesthetic.
If she lives with it
A beautiful mug she reaches for every morning, or a plush that ends up on the couch. These are the gifts that get used, which is the highest compliment a present can get.
The finishing touch
Whatever you choose, a short note explaining why it reminded you of her turns a nice object into a memorable one.