got engaged to her love, Travis Clark, back in April, but now you can finally see the romantic marriage proposal on the Bates family's reality show -- complete with a sweet serenade!On Thursday's season 10 finale, Travis performs the song he wrote for Katie during the unforgettable seaside proposal and only ET has the exclusive first look at the life-changing moment for the young couple.«I'm really going to start crying,» Katie says, wiping away tears as he begins to sing the guitar ballad.