Please see the context here. Paige starts elbowing his dad's abdomen, presumably at full force, for 12 seconds — at 3:02 until 3:14 when Philip Jennings releases Paige. Is this realistic?
Those elbows wouldn't have done anything much at all, even to an untrained person. Most of the time the camera was too high to show her actual elbow, but she seemed too close to hit with the actual point of her elbow anyway, which is the only way the elbow would have even been painful. If it's just the back of her tricep making contact it's very unfocused in space and time and totally meaningless. She wasn't able to rotate her shoulders to generate meaningful power anyway.
(In case you're curious - if she wanted to escape, she could have tried to mix up a few other moves until one worked. Lifting a leg and kicking back at his kneecap might worry him enough to loosen or release his grip, wrapping one leg around the outside of his leg and behind his knee, then pushing off the wall with her other leg might have made him fall over. If she's wearing shoes with a hard heel, kicking backwards into his shins or down onto his toes or instep might have have helped too. Reaching up with her arm and clawing across his face and eyes might have helped (in a street self defence situation that also has the benefit of very obviously marking the attacker: they'll immediately know they're more likely to be caught by the police and maybe shouldn't make it any worse than it already is by continuing the assault). Clasping hands together or wrapping the elbowing arm's fist in the palm of the other hand can also allow the non-elbowing arm to contribute something to the power of an elbow, and might help a girl in that situation. Anything that can create a little space could help her then place a more meaningful elbow, strike to the groin etc.. But there's nothing in the video to suggest she knew what she was doing.)