Yes she is showing early signs and I’m not a dr but she shows signs of bipolar disorder with frequent outbursts and childlike tantrums, but she refuses any medical or mental health help.
Actually, what you are describing sounds more like dementia or early onset Alzheimer's than bipolar. What happens is that the outbursts and childlike tantrums are a sign of frustration due to memory issues. Or at least, that is the way that it was with my dad. If that is the case, then moving back into her old home is probably not in her best interest, because she likely should not be living alone.
However, I can also tell you that if you cater to her a bit more, with kindness and a bit of respect, even when she is being unreasonable it will ease the transition for her.