I didn't realize it until a couple of years ago. But yeah, it is weird that two consecutive albums had "girl" in the title.
I don't find it weird that 2 albums in a row had 'Girl' in it, since they were part of Rihanna's story. The girl from Barbados who made fun Carribean Pop tunes turned into an edgy urban star.
I found it weird that 'girl' was used more than common words.