She kinda has a point I don’t like how she approached it but yeah. Sachi is a little selfish, it’s funny how she said “I do like him, as a friend.” But goes home then finally realizes her feelings the minute she saw her “potential competitor or competition” clinging onto him. Even if she wants to be lover at least she wants him, Sachi knows his feelings yet continue to deny him or at least talk to him so why does she reacts funny when a girl who is much closer to him, HECK even if she had to follow him all the time so close to him? It makes me thinks even though we know the other girl has no chance, Sachi knows if he suddenly doesn’t find her interesting anymore he will go to her? She’s younger, same age group and she’s much closer to him. This is the idea of the many shoujo or romantic mangas.
I'm a bit peeved when the other girl said "You care more about yourself than you care about Keigo". Don't take it out when to others when your crush won't notice you. For me it seems like she cares more fulfilling her desire to be lovers with Keigo than actually wanting to be with him. She's clinging to Keigo in hopes that he would like her back unlike Keigo who actively tries to make Sachi fall for him. This is my opinion tho.