1) Have her behave in wildly erratic ways and offer no explanation/cliché explanations for her (her sister died! Her father didn’t love her!)
2) Make sure she does incredibly stupid things, but continuously remind the reader how smart she really is by having the supporting characters say (ad nauseum), œHow can someone so smart make such stupid decisions?
3)At every opportunity, let her reject help, companionship, and love, then have her brood (late at night, with a glass of scotch”no girlie drinks for our tortured heroine!)about her loneliness
*Too Stupid To Live