It's like this 'relationship' is the fast forwarded version of so many real world couples.
One party is a paranoid control freak, the other is a deceitful sneak - and both are feeding into each other's worst default behaviours.
There's no way Kim is going to be faithful to Stevo once they leave the house, no way! He will sense it, she will lie about it, then he'll check her texts and her phone message history, she'll apologise and say it's 'just friends', he'll complain (rightly) that he can't trust her, she'll complain (rightly) that he's too controlling, he'll get more frenzied and demand she never goes out without telling him where she's going, and eventually she'll **** off back to her ex leaving him devastated. It's absolutely destined to be a shared nightmare.