Ruth's self-esteem and self-confidence all will be at normal levels.
When a teen reaches puberty she has no direct effect on self-esteem or confidence. The kind of looks which changes at this stage can make a person to lose self-esteem.
The best way is a person to take care of herself or himself. Puberty stage is when a girl starts to see some hair in the armpits and on the private parts. Even the voice changes.