I don't know her.

She used to be your best friend, but what happened?

Hyerin was the most nicest person you have met back in middle school till high school, but college changed everything.

Well, ever since in college, delinquents are very common to see, Hyerin made friends with new people because she wanted to meet new people. It didn't worry you at first since you understood it too. But 3 weeks later, Hyerin became different, her style changed, she started wearing clothes that you didn't even know she has, it's like she got it from some of her popular friends, maybe they helped her to buy new things. What makes you concerned is that she doesn't approach you anymore.