Libuše is an Old Czech name. It is derived from adjective libý, the base of which is Slavonic ljub meaning "love", "lovable". Related names are Ljuba, Liběna and Liboslava.
A legendary Czech princess with a prophetic ability was named Libuše. Because this legend is rather old (I think it was first recorded in the beginning of 12th century by the chronicler Kosmas), I believe it isn't just a pet form of Libìna, but more likely simply originating from the same source. ("libý" is a bit ancient Czech word for "pleasant").