What does the ending of the movie "Coherence" mean?

Here's what happens:

- In one reality she hits herself.
- In another reality she hits another her.
- In other alternate realities this repeats.
- She also broke the car glass in one reality.
- Another her also broke the car glass in other alternate realities.
- This is caused by a chain reaction she triggered by her and her actions.

What about her others?

- The one she put in the trunk of the car wakes up in another alternate reality.
- The one she hides in the bathroom wakes up in yet another alternate reality.
- And so on...

At the end:

We see that she has two rings, one she has on, and the other that was in the bathroom that night before she fainted in the hall.

She wakes up and walks outside and see the car glass broken. Then the guy gives her the ring that was left in the bathroom last night. In front of her, that guy receives a call, and that was herself in the beginning of the movie, which moments later arrived at the house and was hit in the bathroom by her at the end.

To summarize, it means that she woke up in an alternate reality, one that the others didn't left the house, one that she only changes places.

I did the analysis based on the movie, similar movies and quantum physics.
More info: Many-worlds interpretation and Director's interview.

The Emily in the last scene is not from that reality. The previous night she's attacked the Emily from that reality and put her in the bathtub. Soon after this she faints. The next morning the Emily from the bathtub is missing... because Beth exits the bathroom. Everyone seems normal which means no one knows of the two Emilys yet. At the same time that reality's Emily has upped and gone away. We don't know why, probably she was freaked out seeing her double. She wasn't dead for sure.

ref : Coherence Explained

Emily Prime wants to replace the Emily from this reality and take on her life and be happy. Emily Prime sneaks up on her double and drugs her. First she throws her in the trunk and later attacks her in the bathroom and puts her in the bathtub. Emily Prime heads to the living room and faints. She wakes up the next morning on the sofa. Looks like the others have not run into the double. At some point the double has gotten up from the bathtub and left. Emily Prime leaves the house and meets Kevin. His phone rings. The call is from Emily. On answering the call, he gives a suspicious look towards Emily Prime and she stares back with guilt. The film ends. The reality that Emily Prime is in now will permanently have 2 Emilys in it. What happens here or in the other realities, well, that’s not part of this film.

Kevin gets a call from that reality's Emily in the end. Initially he picks up the phone thinking someone's playing a joke. Soon as he talks to her on the phone, he realizes something is wrong. She's most definitely alive.

The character of Em is the only one who stays constant. All the other characters are from other realities but Em is always the same Em as at the start of the movie.

At the end, Em discovered that there are so many different realities, and after that blackmail chaos she left the current reality (which is not her). Em visits various realities, which have different different outcomes but most of them are dark. Then, she visits a reality where the people never leave the room. She breaks the car glass, which makes everyone check outside, and gets a chance to tranquilize her (this reality's Em) with some ketamine that she had taken from Beth. But she became conscious again, and a second fight ensued in the bathroom. She killed her or nearly killed her (we can't be sure, because in the morning she disappeared).

At the end, Kevin gives a ring to Em. She finds this ring in the bathroom, and now Em has two rings. After that, Kevin receives a call from another Em. Now this part is left for open interpretation, which Em called Kevin. She may be the same Em who nearly died in the bathroom, or she could be another Em.