Marion Chesney is a popular regency romance author who has also written popular mysteries under this name and also M. C. Beaton. She began her writing with regencies and this is one of a few that Allan Kass illustrated.
The Constant Companion was published by Fawcett in December 1980. I have a March 1987 reprint of this novel. This story is about Constance, who is companion to her beautiful cousin, Amelia. Amelia is determined to marry Lord Philip and is furious when he marries Constance instead.
Allan Kass shows our couple seated on a couch while the evil Amelia looks on. Our heroine is pretty in a pink gown. The couch and her accessories accentuate the pink! Our hero is dashing in formal wear. All three look dressed up to go out to a ball or party. What makes this cover interesting is the striped sofa, the background decorations, and the other lady in purple staring at the couple! I'm always amazed at Allan's detail since you could have eliminated the harp and standing female and it still would have been a great illustration! Soon I will have other Chesney books listed. Enjoy!