Astra said:@Trainerhan:
Chrom marries the woman he's built up the highest amount of support points with at the end of Chapter 12. In the event of a tie, the priority list is: Sumia > Sully > Maribelle > Olivia > Female Avatar. Each time you see a heart come up on top of Chrom and someone else, the two just gained one love point.
Thanks for the info Astra. I will not repeat this mistake ever again.