You can remove a Blink from your favorites in the following way:
iOS
1. From the For You screen, navigate to your Library.
2. Tap on the Favorites icon.
3. Tap on the heart next to the book you would like to remove.
Android
1. Navigate to your Library.
2. Tap on the Favorites icon.
3. Tap on the heart next to the title you would like to remove.