You mention the father coming and going as he pleases, this does more harm than good on a child. You are the only person she has that is stable, so she looks to you for stability and that is probably why she wants you so much. My son is like that too. He wants to be with me all the time. I'm a single mom and his dad is in jail. they learn quickly who is the stable person. I have a five year old boy and I totally understand.
Try to take some time and do some special things with her. Try to focus on positive attention, I know you are tired, me too!! and if she wakes you up during the night, then it has to be really difficult.
She might be going thru some attachment issues too. That can lead to anxiety.
My son comes to my bed at night, he doesn't like to be left alone and is scared of the dark. He says at school he wants me too. You are the pillar of strength for her. It's a hard job to handle too esp when you are tired!!!
I have to let my son know what I am doing and when I will be done and if he needs me he can come to the shower and ask me, but he has to wait until I am donie. Maybe she can play while you in hte shower.
Okay, take a deep breath. Remember that they grow up and she will too, eventually. Parenting is hard and even harder when you are doing it on your own.
Couple of things--- your daughter is still pretty young. She is away from you all day and her wanting to be around you the whole time at home may be part of that. She misses you. And she may be tired as well as she is getting up at night too and waking you. Overly tired kids mean they are harder to deal with. Do you stay very calm when you deal with her . . .? I ask because that is a good way to have our kids stay calm and use nice tones. If we are angry with them, they can mimic that tone themselves. And it sounds terrible coming out of a 6 year olds mouth. Well, it sounds bad for anyone. She also has had a bit of a disruptive life with a dad that comes and goes. That is very hard on a child.
This is a rough year for a lot of kids---- they aren't toddlers anymore and yet they are still young. They have all kinds of expectations placed on them at school that are new and it can be very stressful. It helps to remember what it is like for her as well. She deals with it all with an immature emotional system.
So, I would try to catch her doing things right and praise her like crazy. If she is seeking negative attention, then this switches it to posative attention being much more posative. I'd do a reward chart in which she gets to earn activities with you or something like that. (going to the library and picking out a movie you can watch together, etc.) Make her your helper. Keep it posative and cheerful. When she uses the nasty tone---- tell her you will not talk to her if she uses that tone. Period. And then ignore her until she uses a nice tone and nice words. At night, well------- she is 6. I wouldn't go into her room. If she sits and yells, I would get up one time and say calmly, I am not going to respond again to your yelling. It is time to sleep. And leave. If she gets up, walk her back to her room silently. Say go to sleep. Just don't play when it comes to that stuff. You don't have to yell or get mad. Just be firm.
I'd talk to her a lot more about her feelings. I think that she is showing early signs of anxiety. Getting her to express things to you will help a lot down the road. I don't get all the I'm sorry stuff . . . first she Never says it then she does 10 minutes later and you have too . . . you can work on behavior in other more productive ways. And parents often do have to say sorry-------- my opinion.
Maybe on the weekend, your parents could stay with her for like 2 hours in the afternoon one day so you can go out and have some alone time for you. good luck