Out of print book with "tree" in the title

[Pjcm]

Looking for an out of print book, possibly written during the 1960s or 1970s about a female college student tired of the college men she is dating. I had read a synopsis of this book a few years ago but did not make note of title or author name. Cannot fnd any information now when trying to search amazon or google. From what I can recall, the heroine finds a diary detailng the love affair between a woman and soldier. It turns out the soldier now has memory loss and she finds him, pretending to be his love from the diary entries. As a result of her act, a tragic situation follows. I believe she also gets pregnant. I think the word "tree" is in the title and that it may hav e been written by a man.
Any help would be greatly appreciated.
Thank you.

[Pjcm]

bump

[Rainbowheart]

Was this genre romance, or more literary fiction?

[Pjcm]

I believe the genre was gothic romance or literary fiction.