angry older sibling

[Spandangle]

hiya. my first born daughter is 5 1/2 years and the second 8 weeks old. i had a great relationship with my daughter and she was well behaved until the birth of the baby. she loves the baby and is really helpful and wants to be involved in the care of the baby. BUT she seems really angry and WONT do as she is told..she acts as if she cant hear me. she screams and shouts if she doesnt get her own way, and also lashes out and sometimes bites.
i have involved her with the baby and she bottle feeds her, changes nappies, burps her efc. from the beginning i have made sure that we have plenty of time when it is just me and her - e.g. we will go off swimming together or to the park etc. her behaviour is slightly better during these times but reverts as soon as we are back together as a family. i have also been consistent with puishment but she seems completely unphased by the naughty step/ having toys confiscated etc. i am also making sure i praise up her good behaviour. i cant seem to get through to her or connect with her at all. we used to have really nice conversations and discuss how she felt about things...she wont talk to me now.
any ideas about how to improve this situation has anyone else experienced this? some people hav suggested that i stop punishing her (as i am almost constantly having to discipline her) and instead completely ignore her bad behaviour, so that she is not receiving attention and continue to reward the good? i find it hard to ignore.

She is jealous of the baby. She sounds as if she is trying to be like a baby. She is pobably cross that the baby is with you all day and she has to go to School. I would ignore some of the bas behaviour but not the lashing out and biting,
Try and sit down with her and have a chat, Explian that you don't do anything special with the baby while she is at school as the baby is to young to do things.

It sounds like an attention seeking problem. Guess she was use to it just being her and mummy and now theres another little person on the scene. She may have learnt that being naughty gets her ur attention now, maybe just send her to her room when she's naughty, maybe she will learn that everytime she is naughty she is sent to her room for alone time, she might behave a little better, always explain to her why she is being sent to her room. ignoring her would be difficult and not sure if it entirely healthy. Im sure things will ease up eventually.