my sister has been collecting and opening my mother's post for her while mum is out of the country for a while. she lives about a half hour drive away so is only managing to do it about twice a week. mum currently getting a lot of post, much of it urgent/important as my dad just died and we're trying to sort out all his affairs.
so she took a pile away last night. first thing this morning i had a call saying she'd accidentally opened a letter for the person who lives next door. i should explain the house next door is owned by my mum and rented to a lady and her family to whom we have served notice. two weeks ago when sister arrived to collect the mail 2 policemen were outside the door of the rented property. they told her they couldn't tell her why they were there but the potential charges were serious. sis was cross but we have enough on our plate so didn't pursue, beyond telling letting agent to ensure the property was made secure (door had been forcibly entered).
so the letter she accidentally opened was from the person next doors solicitor. it was addressed to mum's address though. she says she was just opening without looking to see addressee. when she realised what she'd done she stopped reading, but not before finding out some details of the potential crime committed. she doesn't know what to do next. her mistake was an innocent one but she now knows stuff she shouldn't. husband's advice is to put letter back in envelope, reseal and return to sender. however i think she should destroy the letter and the solicitor will chase it and resend if necessary. i think this is probably unreasonable but i'm worried for my sister and if her mistake could get her into trouble.
so am i being unreasonable? and if i am can someone tell me an alternative approach where my sis won't find herself in trouble?