Daughter of the Sun (I thought) was the title.
The book was given by my great grandmother to my mother. My mother is now 60 for reference.
The book was bound in a green fabric with gold accents.
The book was three separate love stories in one book .
Story 1
The first story was Daughter of a Sun. Main characters name is Charlie (Charlotte). Charlie’s father disappears in the mountains and she ends up backpacking with a former student of her fathers through the mountains to solve the mysterious disappearance of her father. They end up finding her father who lives with a lost civilization. Takes place in South America.
Story 2
Woman is an antiques appraiser and falls in love with an engaged client and helps the family find the missing will – that I believe was hidden in a door stop. Takes place in Europe.
Story 3
Gill has arranged marriage with one brother (I think his name starts with an F) and falls in love with the other brother. She fell asleep in the wrong limo and ended up at a castle-like estate. The man she loves did a business merger with her grandfather. Lover calls her mouse. There is a problem with a landslide. Additionally, he is a race car driver. Takes place in Italy
This is the most important book I ever read because it came from my great grandmother. I have no idea who wrote it or if it is even possible to find. I would be humbled by any help.
Could the third story possibly be Unexpected Hazard, by Sophie Weston? In which case this may be a Harlequin anthology.
The first story is “Daughter of the Sun” by Mary Wibberley, Harlequin, published 1978.
If the title “Lure of the Falcon” by Sue Peters sounds familiar, then, together with Ann’s suggestion, these three books are found in a single green and gold bound volume of Harlequin’s “Romance Treasury” series.
On ABE’s site, there’s a copy currently available for under $8 (others are nearer $100). It can be a little tricky to find because of the title variations, so I’ve linked you directly to it… however if the copy has been sold, this will likely become a dead link.
https://www.abebooks.com/servlet/SearchResults?isbn=9780373041374
Otherwise, try searching for a variation of:
“Romance Treasury: Lure of the Falcon, Unexpected Hazard & Daughter of the Sun”
Sue Peters; Sophie Weston; Mary Wibberley
Published by The Romance Treasury Association, 1986
ISBN 10: 0373041373
ISBN 13: 9780373041374
Hardcover, green leather like cloth covered boards; gold design on covers; gold spine title. 574 pages.