Children's behaviors naturally mimic bipolar
Im sure its just the terrible twos, give it time, be firm but loving and see how things go. It all sounds like normal child behaviour.
I tell you that your child is probably okay. She is only two and two year olds are very volatile. They do not understand how to express their emotions like an older child and especially not like an adult. Mood swings and temper tantrums are part of being two. My youngest is three and he is still very volatile. Also, children do have personalities. Some are just calmer than others. My oldest was always calm and had very few outburst. My baby has a temper so if something isn't going his way he will make you know it.
The key is boundaries and consistency. When my three year old is having outbursts we put him in time out. Time is out we put him in his bed in his room and close the door. Of course he knows how to get out, but if he comes out and is still acting up he goes right back in. It takes time and patience. You can't give in or she will think she is the boss.
Things you should worry about for autism are more developmental. Autism is way more than mood.
Is she starting to talk? Has she been babbling or making up her own words up until now? Does she make eye contact with you? (And I mean if she NEVER makes eye contact with you.) These are more signs of autism.
2 years old is a very early age to develop bipolar. Take her to a child psychiatrist and have them make a determination as to what's going on. Some of what you describe could be from behavioral problems that could be discussed with a child psychologist. If it occurs all the time and its more severe they would need to rule out criteria such as autism and the like as that often emerges at that age. Honestly I can't say for sure but a trained child psychiatrist could and it would be well worth speaking to one and see what to do based on what they reccomend.