Within traditional character design, when you're doing one character you don't settle on a single idea first. You try different face shapes, different hair styles, different body types and outfit types. Then you combine your favorites, to make a character. But you probably know all this so I'll digress...
One of the biggest things character designers have to keep in mind is the character's acting ability. That means extremes. Think about the character you have. She's got a really round face, and in one of the drawings you have her mouth open talking. Okay good start, but...what does it look like when her jaw drops in surprise? What about in horror? What does it look like when she scrunches up her face? Let's say someone tricked her and gave her a super bitter or tart candy. What would that look like?
When you play with the extreme's of a characters acting ability you allow yourself a point of reference to dial back from, or extend beyond.
The face isn't the only part of your character that acts though:
Actors use this really cool concept that I think is called "Center of Gravity or Power". It's the idea that if your character has a place that their acting comes from, their body will gravitate to that place. For example: If a character has very stooped over posture, their center of gravity is their feet. That's where all their acting comes from. A good example of this might be the genie from Aladdin. His center of gravity isn't on his person but is extended AROUND him, as though he was in a bubble. His entire method of acting is wild and crazy and swooping and all of that is because his gravity/power is just outside his reach. Characters that have that exuberant and active center will always take up AS MUCH SPACE as possible.
With your character here, I have very little sense of where her acting comes from. She's well drawn, but she's drawn as though you're restraining yourself.
Ultimately when it comes to character sheets and ref, it's all about what you need as an artist. We have to use them constantly on Kamikaze because we have such a broad cast and the continuity has to be right to make our world believable. We can't just change up the character design for no reason.
Anyway, I hope that helps, and hasn't been a huge non-sequitur... 