Ok so my 12 year old daughter is always tired and mopey. how much sleep should she get? or is this just puberty. (has breast buds and discharge )

Need to be checked: 12 years old always tired needs to be evaluated by her pediatrician.She needs at least 7 hours of good sleep.But she needs a physical exam and may need blood test to rule out anemia and other causes of tiredness ib 12 years old.Puberty is a normal ohysiological process and it does not and should not caue tiredness all the time.

Sleep needs: A pubertal child should never get less than 9hr sleep/night & during a growth spurt may need more. After she hits her final height /stage she can get by on 8. The sighs you mention suggest she is entering a rapid growth phase. If she is getting good sleep & is still tired she needs an evaluation. Sluggishness at this age can be caused by a variety of issues.