她总是没自信 怎么说呢

She is always lack of confidence.

She is always no confidence.

she is always not confident in herself.

She is always lack of confidence

She always lacks confidence.(此时lack作动词 也可用lack of 此时作名词 She is always lack of confidence.)

话说...lack不作名词，后面为毛要加of... 自信，self-confidence
she sometimes lacks self-confidence