Why did did Arjun's sister and Sonakshi join hands to ditch him

Arjun Kapoor, Sonakshi Sinha and Anshula Kapoor are great buddies. Thy often hang out together and enjoy each other's company. Is it that Sonakshi has delebarately developed closeness with Anshula to keep her in good spirits? Anyway, the girls were seen enjoying the movie 'Gone Girl' together leaving behind Arjun Kapoor. Recently there were reports that something is brewing between Sona and Arjun. According to the sources, Arjun and Sonakshi, who have recently wrapped up the shooting of 'Tevar', are serious of their relationship. During the shoots the couple was always seen together uttering sweet nothings in each other's ears. Here take a look of the two on the sets of 'Tevar'.