She was convinced that she was still dreaming so she killed herself...
At the end of the film, the focus was shifted on the never-ending spinning totem, which points towards the conclusion that Cobb was still dreaming after all of the occurred events...
So Mal woke up from her dream as she prophesied...Cobb was wrong and continued living in his dream...
They could have lived together in their real lives as they'd planned
So in the end, was Mal right?
That ‘ s what the poor gal felt without a shadow of a doubt (there is an understatement). But at the end of the day, she became utterly delusional... or so some of us think.
With the ending being left *somewhat* ambiguous, one can say that she was right if only YOU thought she was. Myself, I say Cobb managed to come back to reality.
He’s back in the real world, the totem starts to topple right as the camera cuts. If he was still dreaming, the top would never stop spinning. Besides Michael Caine confirmed that the end was real.
shareIt also doesn't matter if the top stops spinning, the top would only continue to spin if he were in someone else's dream, he could still be in his own dream but that was never what the spinning top at the very end was all about, it was a symbol that no matter what Cobb has chosen wherever he is as his reality (he didn't wait for it to stop spinning he just went over to see his children (or his children's projections but to him it doesn't matter)).
Also as someone else pointed out the top was Mal's totem so it might not even work for Cobb, it has also been speculated that Cobb's totem is his wedding ring.
A few reasons why I think he is in the real world: We never see Mal in that level, earlier in the film Cobb was in the same level as the end and the top did stop spinning,