Okay, so I'm guessing she was in love with the neighbor girl and probably thought her feelings were at least a little reciprocated. But not only was that not the case, neighbor girl didn't even really like her. The fact that neighbor girl never talked to Ito after she graduated high school shows she didn't really care about her. So Ito not only found out her love was reciprocated, but also had her, "Don't meet your heroes" moment. Now she's finding herself in a similar situation with Sumika and is doing what she can to pull back.