Lyric discussion by moralclimate 

Cover art for Diamond Smiles lyrics by Boomtown Rats, The

I wonder if it is about Marylin Monroe, hence "Diamond", "they said she did it with grace, they said she did it with style... I remember [her]" and the manner of her death described is metaphorical.

My Interpretation

@moralclimate Bob tells the story that he read a small newspaper article about a young socialite who committed suicide at a party she was at. Somebody described the girl as “the brightest of diamonds” hence Bob got the title from that.