Spoiler alert: End of days
Beta-ed: TattooedLibrarian
Gwen's point of view, be easy on her.
Gwen woke up that morning really happy. Things were finally falling into place. Now she was sure that Rhys loved her, her heart. After all she'd done, all turns and doubts she had finally got it. He was the man to whom she would wake up to each morning. Gwen discovered that she could live with her infidelity. She didn't even hold a grudge against Owen anymore. In a way he helped her to see true value in her life. The morning news disturbed her and Ianto's preaching about doomsday wasn't reassuring. Her fear grew even bigger when she realised that Jack had no answer. The argument with Owen made things even worse, and when she tried to reason with Jack, he attacked her. She let that pass because she wasn't mad at herself anymore.
Talking to Andy who could see right through her was a fine interlude into Bilis's appearance. That man gave her the spooks on a normal day, today she freaked when she saw him. She didn't need her detective hunch to tell her that he was in the middle of it all. After all he was behind Jack and Tosh being sent back in time setting Owen on his path.
Gwen couldn't believe when Jack fired Owen, but she was sure they would sort it out, she would talk to Jack when he calmed down. But then she was left alone with Bilis and everything went to shit. Her fear that she had pushed below the whole day now emerged like a shapeless horror that drowned everything else; no, not Rhys, not now, not now when she finally was able to see him. She felt like she had already lost, she had deserved punishment, but she would beat it, she would protect him at any cost.
Watching him locked away in the vault made her less terrified, but she didn't want to let him out of her sight. When the lights went out she just knew, death had come, her punishment. When she held Rhys's body her mind went blank. She didn't want comfort, touch, anything; she couldn't live like that, alone, no not without Rhys. He laid there empty, cold, she could still hear his laughing and shouting. "Don't answer the phone" when Jack called and she did.
Ianto and Tosh spoke up with their weak voices trying to make her let go of him, but no, this was Rhys Williams and he has to live for her.
"You bring him back" she said to Jack. He is reassuring her whole morning that everything will turn out fine. It's not fine, world ended for her, he had to do something about that or else he's nothing to her.
When she heard him decline her she got furious, why did she ever follow that man? She charged at him with all of her strength but he made her powerless locked in a sympathetic grip. Gwen was too weak to struggle, but then Owen came and touched her. How dare he? She wasn't his to hold, he had no right over her. But when he said that they would open the Rift, he finally made sense. Owen Harper knew loss, and he would help her to get back what was hers. That was the solution, she owed Rhys that much.
Gwen was so focused on her task that she didn't even blink when Owen shot Jack. She didn't really care if Jack would revive or not, the Rift would open and put everything back to normal anyway.