
EDITING TO ADD: I tried this option with my test file. Quicken selected the wrong Cloud file (and old one from my test copy of Quicken 2015) and did not offer me a way to search from my various Cloud accounts and select the most current one.
One question, though: when you say Time Machine wasn't backing up a particular user, are you sure? Time Machine will back up the whole hard drive, including all users on it, unless you have it set to back up only certain folders. So unless you specifically excluded your wife's User folder (or the folder within it that contains her Quicken data file), your Time Machine backup probably does contain the file.