The principal problem you will be up against is competing against smartphone cameras. The next problem you will be up against is that today's prime viewing device for teenagers are smartphone displays. A teenager will be viewing and comparing her results with peers predominantly through that medium, and the typical smartphone cameras and postprocessing apps without much of a user intervention are catering to that medium and have adapted to it very well, covering a whole lot of the "good enough" realm there.
So the main question to ask yourself is what the interest of your daughter may be regarding other media. Nature interest is not the worst for that since you either want rather detailed macro shots or poster-scale wide angle shots. Either are not really a good fit for the limitations inherent in smartphone optics and sensors.
How do the walls in your daughter's room look? Is she one for posters and pictures, and larger scale portraits?
If not, a dedicated camera might appear to her as a cumbersome substitute for an expensive smartphone with optics and electronics as good as they get these days. And there is no turn-off like having no answer to being the girl who drags around pounds of gear because her parents cannot afford a proper smartphone.
At these times and days, starting with film is an expensive endeavor and there is little point in prodding someone to do so who does not feel the desire herself. It seems more effective to learn the basics on digital first.
To differentiate from smartphone photography with regard to the visuals, you want something with a reasonably large sensor and aperture and a detailed image and of course ways to choose all parameters. The basic question is just how high a threshold it will be to wean oneself off the point-and-shoot mode that every digital camera invariably offers.
Another answer proposed just going with a 50mm/F1.8 lens and DSLR and that's it. The problem with that approach is that for landscapes, 50mm is already more "tele" than desirable, particularly so if the DSLR is "APS-C"/"DX" format rather than full-frame, and you will not be able to afford a full-frame anyway. 50mm is a nice portrait/wedding lens, particularly at F1.8.
My own choice for nature shots would be a DSC-R1 which is a "compact" camera (no interchangeable lenses) with APS-C-like sensor from 2005 and consequently somewhat affordable on the used camera market. It has a number of comparatively significant shortcomings, like viewfinder and display not permitting to judge photographic quality without moving to some other device, not-really-great autofocus, bulky size, slow shooting, moderate sensitivity (but not all that dissimilar to film), and with regard to media prices, you'll want to stack 32GB (not larger!) micro-SDHC cards in a micro-SD to Memory-Stick (PRO) Duo adapter within a Memory-Stick Duo to Memory Stick adapter.
However, its sensor and aperture size are large enough that depth-of-focus is a constant issue of attention, it has a sharp and detailed lens going from 24mm effective focal length to 120mm with a manually linked zoom (that's largely preferable over motor zooms), it has excellent color rendition. It doesn't do video at all.
So it tends to be bad in some categories where smartphones are good (particularly size), it has some points where smartphones cannot keep up, it prepares the user to some degree for moving to film eventually (and wasting less time and money on the film basics). And it's great for nature shots.
But it's a dinosaur. Which can be cool or not. But you need buy-in. This is just one proposal: DSLRs of somewhat younger date with a good(!) lens may be a better choice in some regards. To get similar quality, you'll end up paying more and you won't have as much of the retro-chique factor to rely on. How much that ends up a boon or disadvantage is something you need to figure out with your daughter either way. So I strongly suggest involving her into the selection process: she'll have to grit her teeth and survive the comments of her peers, and having involved herself in the choice (even if that involves talking you out of the idea and ending up burying this idea) is certainly one thing that could help.