Comedy in manga is usually pretty broad and over the top. A classroom full of girls changing their look overnight would be the type of goofy thing you’d see in a sitcom aimed at children, and not realistic. But I definitely LOLed
They're going bang and then go back to their lives. He'll still marry the girl, she'll settle with the guy who wants to date her with an eye towards marriage. That's my guess.
She's not stringing him along, she's been clear that he shouldn't be hung up on her. If he chooses to spend time with her, that's his choice. She shouldn't have to literally ban him from her presence. They've been in each other's lives for years.
Same title as the main series but has the subtitle of "Bloom"
Busu ni Hanataba wo. ~Bloom~
Doesn't look like its begun translating yet, hopefully the same scanlators get to it eventually. I love this series!