I realize this is a pretty odious-sounding category, but publisher’s marketing departments, not me, made it up.
Ann Marlowe published three novels of romantic suspense, a genre that was flourishing in the ‘70s (bestselling practitioners were Mary Stewart and Phyllis A. Whitney) but has declined since. No biographical facts could be found on her.

Novels

The Winnowing Winds Dodd Mead 1977.  “This first novel has just enough romance and mystery to fuel younger teenagers’ daydreams.” –School Library Journal

Thunder in the Kerk Dodd Mead 1977 # “A mild, talky little modern gothic.”  --Kirkus

The Red Rockingbird  St. Martin’s Press 1985 # “A better than average romantic adventure”  --Library Journal
Toby Stein is an advertising professional with experience in New York publishing. Having published three works of popular fiction, she turned to non-fiction, assisting less experienced writers.

Born in New York in 1935, she attended Barnard (BA, 1956) and Columbia (MA, 1959).
While studying for her MA, she got an entry-level job in publishing. After a couple of years she switched to advertising. In 1962, she published her first book, a cookbook, with Stein & Day. This connection has been fruitful. In addition to publishing her diet and fitness book, Stein & Day also brought out her novels in paperback. One of the partners in the firm, Sol Stein, is a well-known author, editor, and book packager. He  recommends her on the Web as a “book doctor,” who provides expert editing and rewriting to authors of both fiction and non-fiction. She is listed as co-author of a business book. She lives in New Jersey.

She told LJ that in youth she had not particularly aspired to be a novelist, but became interested in two imagined characters and wrote her first novel about them. Her interest in fiction has lasted. In 2002, she told CA that she was working on a novel.

Novels

All the Time There Is  Random House 1977  Bantam 1978 (pb)* Golden Apple 1984 (pb) * “Easy to dismiss as ‘ladies magazine fiction,’ this first novel is also easy to read, and to like.”  --Library Journal

Getting Together  Atheneum  1980*# Stein & Day 1987 (pb)* “This is basically a coming-of-age novel that deals with commitment in mid-life.”  --Library Journal

Only the Best   Arbor House 1984 Stein & Day 1986 * #

Main sources: Contemporary Authors, writepro.com

Barbara Parker Robinson published one novel with a major publisher. After a long hiatus, she returned to print via the ebook publisher booklocker.com, bringing out a short story collection as well as another novel.
Born in Santa Barbara, she attended Stephens College in Missouri, then moved to northern Virginia, which provided the setting for her first novel.  She now resides in Casa Dorinda, California.
Novels
A Bit of Eden Dutton 1977 * “There is not a single likable character in this dull novel of Southern fox hunting.”  --Library Journal
Croquet Boolocker.com 2002*   “This entertaining novel lets you learn all about the intricate and newly popular British version of the game enjoyed in countless American back yards, while it also explores the dangerous world of dot.com deals gone bad amid the opulence and decay of 1999.”  --user comment, amazon.com

Main source: Speaking of stories.org