Well it might not be Little Mix, but everyone is pretty certain that it is.
The song in question is most likely from their debut album 'DNA'.
The clip itself has roughly 9 seconds of vocals on it, featuring what sounds like Jesy at 00:35 and then Perrie at 01:25.
We've plonked the video below and set it to the appropriate part so you can have a listen yourselves.
You're welcome.