Ah yes, that makes sense! I've left a question on the auction asking her if there's an XS on the frame to indicate its size, as I suspect that's what it will be.

It hadn't occurred to me the wheels might be 24 inch. I'm not so sure I'm keen on them being that small. Still, I might be able to pick it up cheaply enough that I can live with them till I decide whether I like off road cycling enough to upgrade.