你是我的太阳却给了她光芒
[nĭ shì wŏ de tài yáng què jĭ le tā guāng máng]
'You're my sun but giving light to her', expresses that although you were considered central and vital for the user, your attentions and affections have all shifted to another girl instead. The person laments at having been replaced by her while wishing that the beloved can be aware.