Dawg. Have you been reading or not.
She's a black sheep to her family, regardless of romantic feelings for anyone, she's a noble first and foremost and noble women lack any kind of support system when they don't have a family willing to back them up. She's like this because
1. She doesn't even knows what she's feeling abt yulan
2. Marrying the prince (who was once her crush) would literally give her that secure backing.
You saying one is CLEARLY better than another doesn't make it true.
That is true tbh and the only reason i'm saying it this way is because im extremely frustrated by how this story is going (after reading the raws and ln spoilers). From her POV its understandable that you say it that way.
My opinion is more biased as its more of a reader's POV, and the contents are just not worth my time at this point, thats why it came out that way. Not to mention her sister's behaviour later
imo the one whos being indecisive is vio, like bro :U yulan is CLEARLY the better one but once she got the engagement she be like "o, its advantageous for me too" like huh? aite bro dropping this for real