If i understood the last panel well, seems we’re going to the lover’s suicide route huh. Well not surprising, fmc must believes she can’t be happy for a long time anyway, so she wants to end it while it lasts
It's a direct reference to Kuroko's belief that there are no eternal happy endings in real life. She talked about this before.
Traditional shoujo manga almost always end at the peak of happiness for the heroine, but if they were to continue, in her view, they'd never be as happy.
And in Kuroko's logic that means that she'd rather die when she's at her happiest and finally fulfill her dream to be the heroine of her own shoujo manga story so to speak.
If you see this manga from a bird's eye view, it's really about two people who want to be the protagonists of their own stories.
Gomi wants to be a shounen hero, the cool, special guy who saves the heroine.
Kuroko wants to be a shoujo heroine, the princess who gets saved by the prince and lives happily ever after.
Deep down they both actually have really pure and innocent childlike dreams.
The only problem with the latter is that Kuroko thinks this is only achievable in fiction because shoujo stories end right when the couple gets together and are at their happiest. So to replicate it in real life, she has to die at such a moment. Otherwise she will only live to see the happiness crumble (she believes this will always happen because of her years of abuse)