Don't remember the manga, help?

I don't remember the name of the manga but i read a few chapters but the story starts with this girl and her teacher painting her. She loves him but he has no idea, so she consults with her best friend and her best friend says she should give up because he probably has someone else. She was still persistent on confessing to him,so she said for him to meet her at this place on the weekend and she'd wait until he came. She was dresses up in very mature clothes and waited but he didn't come until her parents called for help on searching for her. He found her at around 10 pm or well she waited and he showed up at 10. Anyway he was on the way of bringing her home and she confessed but he said it was bothersome to wear it so he didn't really want to but her pulled out a necklace with a ring on it and said he was engaged. So the next day she went to school and wanted to talk to him about it but she peeks through the door window to the art classroom and sees her best friend and her teacher she loves together and her best friend was about to kiss him! And that's where I stopped. The manga story line is somewhere among this story well based on something similar. Please help me remember the name I'm dying to read it again, thanks!