It wasn’t unexpected. After more than three long years of association with the UPA II coalition government, key ally Mamata Banerjee is taking her name off the lease, packing up her things and getting ready to move out. Whether she has taken Congress’ chances for holding power in India with her depends on how strong — and willing — the party’s other friends are.

This move, precipitated by her anger at urgent government moves to fix India’s economy, is a case of better late than never. There is no point being part of a coalition if you don’t like how it works or the decisions that it makes.

Banerjee isn’t moving out just yet. After giving the coalition 72 hours to relook at its recent initiatives, she has given another 72 hours to the coalition before her ministers resign on Friday, Sept. 21. Her demands: rollback diesel prices, scotch a plan to allow foreign direct investment in India’s retail businesses and spend more money on keeping home cooking gas prices artificially low.

Banerjee accused the UPA of not consulting her on diesel and foreign investment. That’s a fair point, but it’s unclear why she thinks that the coalition will change its mind all of a sudden, when it was all too clear that she has been repeatedly willing to fracture her party’s alliance with the Congress party. This in turn would dramatically improve the chance that Congress’s main rival, the Bharatiya Janata Party, and its allies, could sweep India’s next general elections.

This is her main card to play, that Trinamool is the key to helping Congress fend off the BJP. The question for Congress is whether there might be a call for elections before 2014, and how well the party will weather the vote. For that, it needs other friends, such as the Bahujan Samaj Party (BSP) and Samajwadi Party – Mayawati and Mulayam Singh Yadav – who can make all the difference when its comes to calculating the final numbers in the Lok Sabha.