I can understand how you feel, but perhaps she isn't holding the star hostage so much as saying that without the feature it's only a 4 star app for her.
I recently found a game I like that keeps doing a loud beep every few moves. I love the game, but have to play with the volume turned down because the beeping is so annoying. This keeps me from listening to a. Book or music while I play. I left a similar 4 star review saying that I liked the games, but this issue kept me from rating it higher. I wasn't holding the star hostage, so much as saying without the feature I didn't like the app as much.
Now, having said that, anyone who doesn't give calibre companion 5 stars is an idiot, so I say, make her suffer.
