Adult humans come in more than two sizes.

Although the 559/26" and 622/700c/29" wheel sizes seem eternal, there have always been alternative diameters, both smaller and in-between.
For example, Schwinn made millions of bikes with the S-7/571 and S-6/597 wheel diameters.

Most of the contributors to the recent resurrection of the old French 584/650b/27.5 rim diameter were searching for a Goldilocks "just right" wheel size, in-between 559 and 622, especially with wider tires.

There was a core group of retro-randonneur enthusiasts, trying to keep tires on their specific old rides. So, when folks like Pacenti and Petersen went looking for an in-between size (early 2000s), the Japanese companies (Mitsuboshi, Panaracer) were already producing a few 584 tires.
Pacenti keep advocating for 584 as a MTB size, since 29er wheels (with 2" tires) are too tall for extra-small frames. It grew from there, and now tons of folks are realizing that they have a use for an in-between diameter. 700-to-650-converters (like me), 27+ fat MTBs, hybrids and town bikes, e-bikes, and just mainstream bikes in smaller sizes.

I can't swear that the 584 diameter will last forever, but I believe there will always be a similar "in-between" size.


As for 584/27.5 being a "fad-of-the year" and the "many times more tire choices", that may have seemed true 5 years ago. But 27.5 is elbowing the 559/26" size out of the lineup for many bike and tire makers. For example, Schwalbe is reducing the 559 production of most of its premium tire lines. Some 559/26 tires will be in production for a long time (like Marathons, cruisers, and for cheapo and juvenile MTBs) but the quality choices in 26" are already getting thin.
Perhaps 559 will eventually die, and 571/S-7 will come back as the new hot wheel trend for 2030?


Back to the bike of the OP (@Karina), I believe 26" wheels on her frame would lower it too much.
I agree that she should consider a different bike that fits her better, and bikes designed with 26" wheels would be good candidates.