What was she doing in the Emergency Room? It was almost as if the son tried to commit suicide. Were they getting back together? Someone wrote a review asking these questions, I guess no one would look there and see these are questions.
Velvet Voice
Jennie explains it all in the first few moments of the scene, although it's a bit disjointed and hard to follow, but she went out to blow off the despair over Matt's not wanting to see her, found herself at an art exhibition where she had too many martinis and sprained her ankle.
As far as she and David, no they were not getting back together. His statement after admitting he had always loved her - "That's where it ends" - and her understanding of it indicates that as the story closes, they will be just as they were at its beginning. She'll return to her normal life, and he to his.
Poe! You are...avenged!
Also, Jenny asks David, "Will you stay with me?"
"Yes, I'll stay."
"How long?"
"Until you can stand on your feet again."
Once David has stood in the wings long enough to see Jenny belting out a song to a sold out crowd at the Palladium, he realizes that she is indeed, "on her feet again" and so departs.
One thing about movies: we're always free to imagine for ourselves what took place after the fade-out.
For instance, did Scarlett "think of some way" to get Rhett back? I like to think she did.
In the case of Jenny (I misspelled it before) and David, I imagine that she'd be some part of Matt's life now that the secret is out, occasionally sweeping into London to whisk him off on adventures, like a visiting Auntie Mame (with a fair amount of gently exasperated indulgence from David), and staying in contact in between.
Poe! You are...avenged!