Unfortunately for Lucy, the constituent in question posted screenshots of the original email exchange showing that the email had been "sexed up".
When details were posted in the Telford group on Facebook, Lucy Allan allegedly reported the constituent's Facebook account resulting in it being suspended for a day. Faced with a barrage of negative publicity, Allan first claimed that the last line "Unless you die" was sent in another email before finally admitting that it was taken from someone else's email and added to Rusty's.
Allan is one of this year's new MPs, ousting Labour MP David Wright from his marginal seat in this year's general election. But inexperience is no excuse for breaking the strict MP/Constituent confidentiality or for making up abuse from constituents. It's lucky for Lucy that "Rusty Shackleton" is a pseudonym - not that she knew it at the time - because attributing false comments to somebody that could damage someone's reputation is libel.
"Rusty" has started a petition calling on Lucy Allan to resign which has been suspended while the parliament petitions people "check it meets petition standards". Apparently this might take a few days by which time most people will probably have forgotten about it. Which is convenient.