u/EmmmaSuez

All I can remember is:

1980/90s Australian (or American?) realistic horse chapter book. Blonde girl discovers/furnishes a huge hollow gum tree as a secret home. She discovers or finds a semi-wild palomino horse possibly named Goldie. Cover showed blonde girl and golden horse in realistic western-style art. I gave this book up years ago and now cannot find a trace of it online. I've tried image searching and typing what I know of the plot but nothing has shown up.

Thank you for any help or advice :)