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I think I see two sources of light in her right eye, one up and a larger one down. Did you have a strobe up higher and a reflector down below, or is that a softbox down there?
Typically, you want your main light to be slightly above her, causing a shadow below her chin. Instead, the neck is really lit up and it looks different. I'm going to assume you used a speedlight without a softbox up high, reflector down low. If that's the case, I'd really suggest getting a softbox or shoot-through umbrella to soften the light, and then use the reflector to the opposite side of the main light to reflect light onto the side of her head and hair, fill some of the gaps.
This is especially important when you have a subject with dark or darker hair (like the brunette here) and then your background is dark (black here). Lighting the hair will create separation from the background.