vintage arabian horse/girl book

[pussinboots60]

i am looking for the title or author of a book i read in the 70s. it was about a girl named gabrielle, whose father bought some arabian horses form a man whose daughter , a princess tho she played it down, spent a year in america because her fiance wanted an american educated girl. they go to horse shows, stop in murdo sd, where the time line runs down main street. meet a couple boys, and find out the boy is the girls fiance secretly from arabia (or whatever its called)  any help would be greatly appreciated!! i have tried a couple book searches, but no luck.  thanks so much!!!