But will cloning your wife's installation to the SSD completely overwrite what's already on it is a question for others to answer.
Given sufficient time, money, and desire to obtain the contents of an erased (overwritten) drive, be it SSD or Rotating media the only absolute way to guarantee the data cannot be recovered is to mechanically destroy the drive.
(Think of Frodo, with the unintentional help of Golem, casting the one ring into the volcanic fire from which it was made.)But, as a practical matter, the data would be so difficult (read
EXPEN$IVE) to retrieve in a coherent form the malefactor would have to be convinced there was data worth the cost of retrieval before they would be likely to attempt it. So unless Pendragon's wife has information the disclosure of which is likely to cause
GRAVE damage to the security of the nation or a multi billion dollar institution on her drive just overwriting the data would seem a reasonable risk.
NOTE: With APFS in High Sierra (even without encryption) the recovery task becomes immensely more difficult.
