"She has her hand on her breast." would be possible although I think for the female breast "seno" is preferable.
- his hand on her breast or her hand on his breast instead are not correct. With parts of the body and clothing you can omit the possessive pronoun only if the part of the body/clothing belongs to the subject. (obviously without further context)
Ho preso il portafoglio. I have taken my wallet.
Ho preso il tuo portafoglio. I have taken your wallet.
Ha una mano sul petto (so without possessive pronoun it's her hand on her chest or his hand on his chest or a hand on his/her chest)
sandrabruck: I've got to hand it to you - you really keep abreast of these things well, earning a lingot for skirting the tricky issue of what HIS hand is doing on HER breast in the first place. For my part, I think he should keep his hands to himself and turn his attention to learning Italian. . On the other hand the sentence gives added meaning to the phrase "hands on learning".
No, "mettersi una mano sul petto/sul cuore " is similar to "hand on heart" .. be honest, be loyal
If you want to check Italian proverbs "modo di dire" you can use the wonderful site of the journal "corriere della sera" .. on which you can search by keywords (tipo "mano" "cuore" "petto").. Unfortunately it's entirely in Italian.
"mettersi una mano sul petto":