Her sentence was clearly an outburst of anger, even though she said it relatively calmly, Marco must have done something that hurt her a lot for her to give him an ultimatum like that.

The bargaining stage differs from person to person but it's kind of similar to the denial stage with the difference that this time you are in denial about your lack of power and influence over the circumstances, rather than the cause of grief itself.

You feel like you can bargain for a better deal but you aren't in a position to do so.

Your terminal illness isn't going away just because you promise to live a healthier life style and your ex won't come back just because you tell them that you are going to be different from now on.

Stage 4 is when you realize how powerless you are and how inevitable the thing that causes you grief is and that there's no hope to change things for the better, thus depression kicks in. It's the second time you have to face the shock that your picture of reality contradicts actual reality, the first time was after the denial phase when you reacted with anger but now you can't even muster enough energy to be angry about it anymore.

In my given example for stage 3, Star would be no longer in denial that she has lost Marco to Jackie but she'd still be clinging to the hope that there is some way she can change the fact and that it's not too late for her to be with Marco after all.