OH MY GOD I LOVE THIS SO MUCH!! I really love Abel for Mia. I hope this isn't second lead syndrome or else I'll cry for real. T_T
With that said, Prince Sion looks like a really nice guy and if ever Mia does end up with Abel, I hope they don't make Sion up to be some kind of behind-the-scenes evil dude. (Most isekais for some reason somehow need to justify the "perfect dude" not being chosen)
It doesn't have to be like that honestly. They could just stay as friends or graciously accept not being with FL.