your sister is lucky to have someone like you on her side. i congradulate you for for caring. in your post, you said that your sister has been prescribed lithium since november. but you never say who did the rx. is it her medical dr, gp, psychiatrist, or therapist? only a trained and experienced psychiatrist (imho) can make a proper diagnosis of bp and decide which, out of several, mood stabelizers to prescribe.
my normal stae is depressive, with the odd manic binges. i have been on lithium since 2001 and on welbutrin since last year. i changed pdocs because i felt that the other one wasn't really interested in my health anymoire - io had become "routine."
also be aware that lithium, as a mood stabelizer, is also used for a multitude of mental illnesses including schizophrenia and schizoeffective bahavior.
i hope that this helps you. i admire your caring and your courage.
That light at the end of he tunnel? It's an on-coming train.