Board Thread:Questions and Answers/@comment-30609878-20180513084342/@comment-193.127.223.11-20180514071217

One can also use Fleet Library in-game, scroll trough and get the index numbers of shipgirls they do not own (cards won't show up) then check it up with wiki here.

Of course this only works if you never owned said shipgirl, because their library entry is made upon aquisition.