Idk to me it read more like Chiharu let an opportunity to get with Mei pass cause she was scared of commitment or changing their relationship or such, and now she feels like she isn't worthy of being with Mei because she chickened out when it mattered. She loves Mei so much she thinks she deserves better than the coward Chiharu sees herself as.
But I'm not ace so maybe i just didn't get it idk.