The Accidental Highland Hero — Terry Spear

Lady Eilis Dunbarton didn't think life could get any worse, until her loving cousin dies and Eilis learns she is to wed the man her cousin was to marry. Not by a change of contract, though. Instead, by deceit. If he learns she is not her cousin, Agnes, her life is forfeit. Crossing the Irish Sea, her ship sinks, she survives, but temporarily loses her memories. When a Highland Clan takes her in, she remembers one thing. She must flee at all costs and disappear. She knows if her family learns of her whereabouts, her life is over.

James MacNeill must take a bride or give up his holdings to one of his younger brothers. Malcolm has already taken to wife, the fair Lady Anice of Brecken. Dougald is the next one in line to govern the MacNeill Clan if James does not wed and provide an heir. But when James discovers his cousin and advisor have rescued a half-drowned lass from the sea, there's speculation she is of the enemy clan. Returning her to them is his plan, since he has no intention of using one of their lasses as a bargaining tool. But his mother has another notion -- use the lass as a means to entice one of the ladies he is interested in marrying, to visit him and commit to marriage. And then return her to her clan, if she is agreeable.

Only nothing works out as anyone plans.