Angie being goofy energetic for the first time is so cute. This poor girl deserves better than Julian (and probably Leon despite his being a badass, if we're honest about his personality).
Leon has the right idea though. The best revenge is to become so fulfilled and happy that, when everything eventually catches up to that stupid prince and it all comes crashing down-when he comes back to you in tears because you continue to be a wonderful person, you're able to give a sincere and happy smile as you reply "Not a chance".
There's technically nothing stopping Leon from starting a relationship with Olivia. She's a commoner, but he can still marry her as a noble if he feels like it. What's the worst that could happen? Losing his standing like he wants?
As for the future saint thing...well, that's the future. If anything, get in while she's still eligible. People can't complain about you dating above your standing when the situation was previously reversed.