My 12 year old cousin got her periods twice this month but she usually gets them once a month, is this normal for her ?

Maybe: Especially in young adolescents, it is normal to have irregular periods for the first year or two after menarche (first period). I wouldnt be particularly concerned unless the bleeding is heavy and prolonged and could lead to anemia.

Menstrsal cycle: The answer would depend on when she actually started her first period . Most cycles are not regular for about 12-18 months

Hormone regulation: During early menses cycles may be irregular because of hormone regulation. Have her checked for assessment of her general health and insure that she is not loosing too much blood. Continue to monitor her cycles. Sometimes hormone therapy is required. All the best with her care.

Yes could be: this is not at all unusual at this age particularly at the start of menstruation.

Periods : It would depend on when she started her periods ... It is not uncommon to have a period that is not regular for 12-18 months

Depends: A female's cycle can be highly irregular for the first year or so.

It happens: The first year or so young women may not ovulate (release an egg) during their cycle. Releasing the egg is part of what makes periods regular.This makes early cycles irregular in both timing and amount of flow. After 6m to a year most begin regular ovulation and the issue resolves. A few women go on to have cycle irregularity as their pattern.