Does anyone know what this song is and the rest of the lyrics?

My aunt is 80. She has dementia. Her memory for day to day things is going but it is clear for 60 years ago. She sings old songs but can't remember the title or all the words. Could you help? This is a song she keeps singing, words so far seem to be,

Don't say those words if you don't mean it,

Don't say those words if they aren't true,

Don't tear my heart it's made of paper,

because my heart loves only you.

I would be grateful for the title, the artist or the rest of the lyrics.

Thank you, hope you can help.