Charming? Maybe funny? Attractive? And good in bed i think,,, ari is also a spoiled only child so she'd act like that to those who she thinks is 'below' her
It's because Ari is young and immature. She's in the phase where superficial things really matter to her like materialistic things, good looking boyfriend, anything that boosts her ego, etc. So having someone chase her who's good looking, charming, and a lot older than her made her feel like she got a good catch.
Thats why if you noticed, all of her insecurities are superficial: minshit doesnt buy her luxury things, she made a post comparing her APPARANCE with Minshit's ex basically asking who's better. The things she listed are all superficial, nothing about how Haesoo might have treated minshit. (These insecurities occur to everyone but I'm not saying all of them are superficial. It's just that Ari is highly fixated on these things specifically, bc she's in the phase where these are her priorities)
Also that time when she asked minshit why he left haesoo. He answered because she's infertile and her reaction was literally "wtf that's it"? This really shows that she's still immature and in the stage where her priorities are different
If your partner isn't making you feel secured of their love for you, then leave. There's no point of staying into a relationship that makes you feel insecure or bother over their ex lover. A secured person wouldn't care over their partner's ex lover. Lol
But seriously tho, is Mincheol even worth it? Aside from his looks, is there something in him that can gives justification for Ari to act like that? I can't even consider him a good catch since he got no money in him. Lol