Just Found Out My 15 Yr Old Granddaughter Is Going

Just found out my 15 yr old granddaughter is going on 250 mg metformin(?) for diabetes......changing her diet and exercise...she has been having issues with periods, weight gain, etc, even though she eats less then her younger sister who is 12d......what can I do to help her other than exercise and eat what she does? She is going through a difficult age group as it is...I want to support her and need to understand what to do for her.
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