Wow, is this post an aberration...
For one, I would be more concerned with the fact that you are introducing exogenous androgens into a female body - that alone bears a cascade of side-effects.
Secondly, human body has many feedback mechanism, the ones you should worry about are the feedback loops - they are dennotative of negative side-effects. That said, exogenous hormones can alter neurochemistry in a MALE body. In a female body the changes are very much unpredictable, and coupled with bipolar disorder are very much UNexplored. BTW, is she a manic depressive (type I) or hypomanic depressive (type II).
Thirdly, why not try milder substances/precursors. I know this is anabolic board, and if it's legal you don't like it, but trying low dose 19-nor or OHN (nandrolones) or even 1,4-andro (boldenone precursor) could provide for initial indicators of alteration in behavior and otherwise BEFORE you administer something along the lines of oxandrolone/methenolone. I know women who have tried pro-hormones with impressive results and virtually no side-effects (lower dosages of course).
I think this has been asked - is she being treated for her condition? What does her drug-rx regimen include (if anything)?