No. It feels better to the person than the depression, but it's still part of the pathology. If it's true bipolar, as far as I know the only treatment is medication, though I might be wrong about that -- everybody is usually wrong about everything! But the mania lasts for awhile and then turns into the depression. Two sides of the same coin.
No....it is not. It is still bi-polar, just another symptom of the disorder. It is called "mania". It is important that the person gets medication to correct things. A therapist can also help a lot and tracking the mood as well (recording triggers etc etc). I must commend you on your patience. Not a lot of people could put up with it but you seem to be handling things as best as you know how.
Re the baby sitting, I am not so sure that is a great idea. Perhaps, if it is supervised baby sitting, not necessarily sitting over her but just being present in the house would be better. As Paxiled outlined, the mania does not last, it will eventually turn to a very down feeling.
Peace and Love,