I suggest you use the ‘Clone Any Record’ plugin available from the Plugin Store.
Select the current sister Individual record and run the plugin, which provides a Result Set of all the new cloned data.
That will produce an almost identical ‘twin’ sister with the same parents and all the same Individual facts except as outlined below.
This new ‘twin’ will NOT be linked to the husband of the original sister.
Therefore, she will NOT have any Family events such as Marriage nor any Children.
Also, she will NOT be a Fact Witness to any facts.
However, that should save you a great deal of work.
If you are unsatisfied with what the plugin produces, immediately use the Edit > Undo Plugin Updates command or the File > Backup/Restore > Revert to Snapshot command.
Regards, Mike Tate