Lady Tara is the last book by Leonora Blythe illustrated by Allan Kass that I own. It was published by Fawcett in 1978. It is the story of Lady Tara, who is masquerading as a highwayman when she holds up Lord Raven's coach. This embroils him into her dangerous mission!
Allan Kass paints the scene of the holdup and we see our couple in an embrace despite the pistol she holds and her accessory holds in the background! Our hero is dashing in a red long jacket with his hair in a queue, which denotes this to be pre-regency times while she is dressed as a psuedo-highwayman! Note her long red hair which must have escaped her hat! It is an improbable, but fun illustration!