How to support my friend whom has bipolar disorder . her mood is still very unstable even on medication?

Natural intervention: There are no biological markers for the diagnoses of bipolar disorder or the other psychiatric disorders & so such a diagnosis is never for certain. Furthermore, there are a myriad of possible side effects from the psychiatric drugs, many of which mimic mental illness. So for a start I encourage you to have your friend examined by a Family Doctor or Internist to rule out any medical conditions.