@Kendama
I hadn't considered it too much but the divorce route might actually be a good plan for her if she can pull it off properly right now and actually convinces the empress to help her since it could also backfire extremely easily.
1) Plant rumours to flip the script and say that the prince is actually the one cheating on her
2) Get divorce on the grounds of it being a loveless marriage (that's not even been consummated?)
3) Prince wastes time chasing after her instead of taking the throne which makes it look like the rumours about him cheating are all true while the first prince is propped onto the throne.
The problem with this plan is whether or not anyone considers Canaria's personal will instead of assuming she's a puppet like usual as it would look like she's trying to trick them into helping her make her husband into the emperor.