Willow by Sahara Kelly

Willow, (Holly’s not-identical twin), is the last unwed member of the Trease family. She missed the Christmas holiday with her family at Forest Grange, since an unexpected incident led to her caring for her old French mistress on the south coast. A sad ending leaves Willow with a promise she must honour, and in possession of a little cottage on the shore. To complicate matters, a large bundle dumped at her door turns out to be a man with a dangerous fever, not to mention a severely sprained ankle.
And she knows him.
When Harry Chalmers awakens to find his nurse is none other than Willow Trease, sister of his best friend, he’s stunned, confused, and profoundly concerned, since his business is not something he can share with Willow. He’s even more surprised when he learns of the creative way she has handled his presence. It’s also a huge risk for both of them.
But he’s helpless and completely reliant on her care, even though he knows he must return to London as soon as possible. After that business is concluded, he can turn his attention to repairing any damage Willow’s hasty assertion may have caused.