It is always difficult to give advice to a friend of a friend of a friend.
Thus we can only talk in terms of generalities.
I would guess that your friend suffers from endogenous depression and that there may even be a gene running in the family that predisposes them to be depressed.
Most doctors would treat that with drugs, but because I believe that drugs can only treat symptoms not causes, I am more interested in treating the underlying causes without recourse to drugs.
Most people with depression are found to be hypoglycemic - a nutritional disorder - that can be treated by adopting the hypoglycemic diet.
This can be tested with a special medical test for hypoglycemia as described at our web site. Search our web site for “testing for hypoglycemia...”.
The best is to contact a complementary doctor familiar with nutritional medicine or perhaps a nutritionist or holistic counsellor.
Thus all I can say at this stage that she is probably hypoglycemic and that going on a hypoglycemic diet will stabilize her mood swings. Later on she may benefit from some psychotherapy.
Jurriaan plesman, ba(psych), post grad. Dip. Clin. Nutr.