Suzy is the same girl who cried her heart out after watching 'Bajrangi Bhaijaan' that was high on emotional content. Apparently, the lucky girl even got to meet her favourite star and was a frequent visitor on the sets of 'Sultan.' Salman, who had developed a great bond with Suzy felt that she resembles Anushka a lot and would perfectly fit the role of the latter's younger version in the film.
So Salman Khan chose Suzy to play younger Anushka in 'Sultan'.