In the Unlikely Event by L.J. Shen

Rory travels overseas to Ireland to try to get some closure on the father she never met. But everyone she meets only seem to make her ask more questions and understand less of the man he was. Then she meets Malachy, she has never met a more infuriating human. That is until she meets her half sister who hates her and wants nothing to do with her. But she can't pull her self away from Mal! Rory falls into a world she never knew existed, she can't look away from him or ignore how he makes her feel. But she's leaving tomorrow and has all the responsibilities in America and can't fall for a man in Ireland. Or can she?