http://www.imdb.com/title/tt4477536/ratings
Almost half the votes are fake 1*/10*. Without them the rating would be near 5.5. Men rate it 3.3 and Women 6.0.
The highest group is not older women, but teenage girls at 6.8! Rated 18A in US.
Trolls are posting fake 1* reviews, real reviews are mixed.
As someone who finished highschool few years ago, this doesn't suprise me. There was a group of fangirls reading 50 Shades in my class that also went to see it when it was in theaters. Funny thing being that it was probably one of the few, if not the only book they actually read during their entire time in highschool.
So yeah, it figures that demographic that gave us the majority of Bieber fans also gave this the highest rating.