So frustrated with 6 y.o.

This is my first post. I joined specifically to get advice on this situation because I am SO frustrated!!

I live with my boyfriend and his 6 year old daughter. He has primary custody of her so she is with us all of the time except for spring break and summer break. He works A LOT and I stay home to take care of her. We used to have a REALLY good relationship. We were so close and I really enjoyed doing things with her. I have my education degree, I worked in a day care for 3 years, I used to babysit, etc. I LOVE kids and can't wait to have kids of my own. However, she has been driving me crazy recently. Last year when she was 5 was when we had a really good relationship. This was when I was just moving into the house. She had no responsibilities at this time besides to go to bed (but even that wasn't very strictly enforced.) My boyfriend had a nanny prior to me moving in and she let his daughter basically do whatever she wanted and so did he.

Well since I have moved in and she has started kindergarten it has taken a turn for the worse. She has responsibilities and I am the one that has to enforce those and she hates it. When I ask her to do homework, she throws a tantrum everytime and ends up in timeout. When she has to eat dinner, if it isn't junk food, another tantrum occurs. So my reaction was that she would go to bed without dinner. Then, my boyfriend would feel bad and take her food up. Or if she misbehaved, I would take away treats only later to find out he sneaked her some. This frustrated me SO much so I told him we needed to get on the same page or this was never going to work.

He works so much that she rarely sees him so a lot of her behavior is in response to this. However, he has to work this schedule for right now. He is a musician so he can go from working a ton to nothing very quickly if he doesn't keep up his schedule. I just can't take it anymore though. I used to be so calm but I find myself losing it now. I yell, send her to her room, I get frustrated, take things away, and no longer have the desire to do things with her. I feel bad because I am starting to build up resentment because I do SO much for her and I get taken advantage of and treated with disrespect.

I have started a new system. We have house rules, and a chart with responsibilities. Each responsibility earns a set amount of pennies (from 1-3 depending on the responsibility). The other side of the chart states privileges and how much pennies they are worth. She can earn 23 pennies a day. 2/3 of those pennies are to be spent "buying" privileges that day and the other 1/3 are saved up for long term, bigger things. If she doesn't complete her responsibilities the FIRST time I ask, without throwing a fit, she gets those pennies deducted from her bank. If she does complete the task, then she earns those pennies. This weekend, she hadn't earned enough pennies to go to the movies on Friday. My boyfriend was trying to find things to do for her to earn more pennies so we could go, but that's not the point. IMO, she didn't earn the pennies, she doesn't go to the movies. So she didn't. This is the first week we started this system and it seemed to be working, however today, as soon as her Dad leaves I ask her to start her homework and she says she can't find it. I told her she had to look for it and she starts crying and throwing a fit. It has now been an hour and she is up in her room still crying, no homework done. I am going to send her to school tomorrow with her homework not done and she can explain to her teachers why. I had her all day today and took her out for slurpees, played outside all day, bought her new crayons, etc. Her dad was home for 1 hour this afternoon then left again and as soon as he does she starts with the fits.