Reaching out and hoping someone might know this one… I’m not sure if it was published in the mid/late 80s or early 90s – I remember reading it when I was 10 or so, and that would’ve been 1995, but it belong to my older sister, who was 15 in 1995 so I think it must’ve been late 80s or first part of the 90s, as she wasn’t reading it around 15. It was a fantasy novel, something about a young girl who goes on a journey (I don’t remember what for!) but I know there was some time where she was riding a horse (or maybe a unicorn), and there’s a scene where she’s crossing a big field, and I’m thinking there might have been a dragon in it somewhere. I actually can sort of see the cover in my head too… it was a metallic sheen – green/tealish and had a girl (and maybe the horse/unicorn) on the cover. I LOVED that book and my searches have led to ZERO results because it’s so very vague. Suggestion: The Blue Sword By Robin McKinley
Second Suggestion: Song of the Wanderer by Bruce Coville
Third suggestion from Lost Classics reader Jacalyn: could be The Realms of the Gods by Tamora Pierce or like a mix of all the books in that series by her- The Immortals.