Who is the person that Gwen sees?

Dr. Olivia "Liv" Octavius

"Who are you?" said the bushy-haired woman who was aiming a gun in Gwen's direction. "Why do you pretend to recognize me? I have never seen you before in my life."

"I'm sorry, Dr. Octavius," said Gwen. "My name is Gwen Stacy. I come from a distant er- country and I recognized you from an old magazine article."

"Oh, really," said Dr. Octavius. "What magazine?"

"I don't remember," said Gwen. "However, I do remember it saying something about your work in advanced quantum physics and how you wanted to someday invent a method of interdimensional travel."

"Oh, really?" said Dr. Octavius. "That sounds like a rather interesting article. It's a shame I've never heard of it. But then you didn't come here from a distant country, did you? You came here from an alternative universe."

"How did you know?" asked Gwen.

"I get visitors from alternative universes all the time," said Dr. Octavius. "Usually it's that annoying fellow in the blue police box. Sometimes it's that equally annoying Sam Beckett. Many times it's that silly Clara Oswald and her friend Me. Once I even got a visit from some teenager in a gray DeLorean. So where do you come from? Some universe where the women your age don't wear clothes, I'd imagine."

"Well, actually..." Gwen started to say.

"It doesn't matter," said Dr. Octavius. "If you're like most such visitors, you're going to start glitching pretty soon and you might need my help. Especially if you wish to go home again."

"So you'll help me?" asked Gwen.

Dr. Octavius just smiled. "Not a chance."