She is the child.  Put your foot down. At 3 yo she should be in bed at 7:30 or 8 pm the latest.  Your BF should not be working leaving the kid for you to take care of.  When your BF is working your rules apply,  if get She punches you in the stomach she get punished, goes into her room no toys no nothing.  If said you not my mother. She goes In her room for Disrespecting you.  You know her better you know what to take away.  If BF complain then he gets a sitter for her 

OK, take a deep breath. She is 3. I'm afraid, that with some kids in particular, this is pretty common behaviour. They are old enough to know that they are a separate person, but obviously not old enough to do things responsibily. They are using their new found ability to articulate their wishes and just being horrible. It shouldn't be the terrible twos it should be the terrible 3s. My bio son said things like this to me when he was that age. He used to tell me I was fired. Ha ha.  They KIND OF know what they are doing, but they are really way too young to fully understand the impact of what they're doing on other people. They just don't have the mental capacity to know how hurtful the things they say are. Not saying they don't know it doesn't have impact - of course they do, they do it to get a reaction, but they simply do not have the mental sophistication to really understand about other people's feelings or needs. 

It is really difficult to stay calm and in control, but this is what you have to do. Parenting isn't just about the happy moments. It's about when they're being little shits, too.  And I hate to say it, but she is probably testing you. You are now her main mother figure, her real mother left her and she is probably subconsciously testing you to see if you are really there for her no matter what. She is going through some major trauma and that WILL impact her behaviour. 

I will say this though - you MUST NOT hit her. EVER. She is not your child. You have to find other ways to discipline her. 1) I don't think that this is good parenting and 2) you could get in legal trouble. I get it, I did spank my bio son, but this was my failure as a parent not a good parenting approach.  I did not do it often and never in anger, but it was the thing that worked for him because he is stubborn like his mother.  I always always always used the supernanny approach - (not that she would condone hitting!) - but her - warning, countdown, consequence - before I spanked him. He has never just been slapped (by me) out of the blue without a verbal warning. And this works so much better because even now years later and I haven't hit him in years and years and the countdown still works! 

At 3 you have to give them a warning and an opportunity to stop doing what they're doing or start doing what they should be doing (e.g. teeth brushing, etc).

Also - why are you doing all this childcare?  I do childcare for my boyfriend sometimes and in a couple of weeks I will have to watch his kids while he works, but he watches my son for me. 

Agree with what others have said. I also think that she is testing you. 3 is an age when they are looking for boundaries. Boundaries make them feel more secure. Just be consistent with her and ignore the 'i dont love you' stuff, she is looking for a reaction.

And yes, she should be in bed long before 11pm. 7-8 is the time so tbat she gets enough sleep consistent with her age. Not enough sleep makes children irritable and difficult to handle.

Where is the mother and why is she not present in the child's life?