I suspect it was just a PR planted rumour. Nobody would offer her main lead in that phase, in a commercial film opposite Khans.
Farah generally works with younger actresses. Sushmita is probably the only senior actress Farah cast in her film.
Anyway if rumour is true then it is clear she is under pressure of her in laws or failure of Abhishek which is why she rejects roles if not paired with Abhishek in same film. Probably wants to avoid embarrassment of Dhoom 2 which upset her MIL a lot.
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