The biggest rival in a relationship is someone from the past. So let him finish with his past first, before you enter his life
But for Sean, Rhea will never be finished with her past. Rhea's love is only for her deceased boyfriend. Sean does not require Rhea to forget her past, what the guy wants is to see the girl he likes happy.
For Rhea herself, falling in love is not something she can control. She cannot choose who she should fall in love with, because it is her heart that chooses. When her heart has chosen, Rhea will not be able to refuse it.
"I will continue to wait for you. And I will not give up before you fall in love with me" - Arseandrio Rahendra