Sometimes characters spring to life easily through your fingertips and other times they kind of plod out without much fanfare or dimension. If you're halfway through with your story or struggling to get it going, go back to character. Even if you have a thin plot, you can make a character-driven novel interesting and gripping, as long as you make your MC someone worthy to read about and follow.You may need to go back to the character drafting board.
You already have your who, but have you asked "what" questions? What questions are pretty generic, just digging into the surface of desire and motivation.
What does she want most?
What is or will be her biggest obstacle in getting it? Internal and external.
What does she do under pressure?
What does she fear most?
What secondary things does she want?
What will stand in her way at getting those desires?
What does she regret, dream about, fixate on, run to or escape with?
What habits enhance or hinder her choices and actions?
Once you've answered several "what" questions, you can delve deeper into the psyche by answering the "whys".
Why does she want to dye her hair pink? Why pink, why not auburn?
Why does she hate her father?
Why does she believe she'll never find love?
Why is her room painted black?
Why does she want revenge?
Answering those questions will give you a more fully developed character and spawn other questions and surprise you with things you didn't know. Once you know who your character is, what they want and why, brainstorm the hows, which takes everything you learn and puts it into action. Discovering the hows is the best way you show character rather than tell.
How will she get the attention of the millionaire when he has that selfish twit Bambi on his arm?
How will she get home or to some place safe when her car dies in the middle of nowhere, at night?
How will she get away from her kidnappers?
How will she accomplish her goal?
How will she deal with moving to a new locale?
It makes an even better story if your characters fail in their hows, if things go awry or set her three steps back. So brainstorm the "hows" of destruction and deterrence as well.
Once you answer questions as such, your characters will cease to be flat; they'll be well-rounded and seemingly real, and in knowing them so deeply, you'll then be able to build a more gripping plot in the same creative breath. Anyone can tell the difference between a stick figure and a flesh-and-blood person. Aim to create characters on the later end of the spectrum, then those babies of yours will be unforgettable.
~ Signing off and sending out cyber hugs.