我没有你心里的那个她单纯
[wŏ méi yŏu nĭ xīn lĭ de nèi gè tā dān chún]
Translates as 'I'm not as simple-minded as her in your heart.' Here, it shows someone feels they cannot match another person in their beloved's eyes, maybe acknowledging the other's simplicity and the speaker's deeper understanding or awareness.