An Engagement of Convenience: Harlequin comics

At a class reunion of her prestigious girl's high school, Harriet is reunited with Rosa, a girl who looks just like her despite the fact that they aren't related. The two of them get along like twins and confide in each other. And then in order to resolve both their problems, they come up with a strange master plan! Harriet will go to Tuscany for Rosa's grandmother's birthday celebration and pose as Rosa. It'll be fine. Rosa has a cousin who has always been taken with her, and Harriet had better not let this head of a noble family find out who she really is...!