I am single parent of two adorable little girls the oldest being nearly 6 and the youngest is 9 months. My eldest is acting out and she’s getting worse.
I think a lot of it is attention as she has my undivided attention for nearly 5 years,

I’ve tried everything and nothing is working, her behavior is getting out of hand and I’m stuck at what to do. I’m starting to lose patience with her, I don’t hit her and I’ve been consistent with time-out, shouting, taking toys etc. etc. I’ve explained to her that she won’t get as much attention as she did as she has a little sister now, she is also lying about little things.

She is normally very well-mannered and hardly ever acts out. I try and spread my attention between them both on top of trying to do house work etc. I need help.

Is she in day care? That might do wonders. How about a play group, or a shared parenting group? I agree that all the undivided attention she got is behind all this, and it will be infinitely easier to solve in groups than at just at home.

I was four when my little brother was born, and my older son was 4.5 when his brother was born. Avoid all the "don't" and "can't" sentences. When you are fussing with the baby, talk to the older child and get her to make up stories with you. If you are feeding the baby, have her read to you (or at least make up stories about the pictures in the book) and let her hold up the book so you can read to her. In other words, pay attention to her because it sounds like she is being naughty to get your negative attention, which at least is something. Ask her opinion about stuff, even about the baby -- "Do you think it's cold enough today that Little Sara should wear a sweater?" etc. Does the older child have a special doll? Maybe she can diaper and dress the doll while you do the same with Baby. But let her help you fold the linens and towels and match clean socks and fold underwear and all the baby things too. And be chatty with her, smiling, bubbly, and enthusiastic. The baby won't care, but your older child will bathe in the positive attention you are giving her

I think would help if you have at least one or 2 nights and spend time with them, even take them out to eat if you can afford it. Spending time with your kids is important cause they will act up if you don't. Even sit down or do something with your kids even if its an hour at night time. If this don't help I would say you probley need a dare care for your kids.Maybe even get your kids a little surprise when you come home. Tell them you will bring home a surprise once a week if you obey the babysitter. I know from exprerience because I am a babysitter and I've delt with this before and all they need is hour worth of attention from the parent at least at night time and maybe a little surprise once a week if they obey the sitter.

Include her in chores and make her moms little helper and lavish her with praise. She will love it.

Is she in school? At 5, almost 6, she should be in Kindergarten.