The registration for the sept 2011 primary school intake opens on the 1st of september and I'm in 2 minds over applying for Aoife to go

I've always said that I would register her and send her the earliest I could for purely selfish reasons but now the time is nearly here I'm worried that it will be the wrong thing to do. I was a july baby and started reception the september following my 4th birthday, luckily I was a reasonably bright student so never fell behind though at the same time I was not ahead either ...... I was reading on another forum about what is better for a child with regards to the month they were born and the age of starting school and it seems most people would have preferred their children to have been born in september and start school at 5, reasons include a more mature child, better chance of doing well at school and an extra year at home.
Aoife is a bright girl and I feel awful that she is stuck at home with me ALL the time, I was fortunate in one respect that I was able to work part time after having her and had my sister to look after her while I worked but it mean't she did not go to nursery so has never had the chance to play with other children or get out of the house away from us

. I missed applying for her to go to nursery this september as the whole of feb all I could do to was try to stay awake or not feel sick so she is stuck at home for another year.
Aoife adores playing with other children at park if she sees them and is always talking about her friends which breaks my heart as her only friend is Imogen
Okay this has turned into essay which is

what I want to know is will I really be emotionally and educationally harming her by sending her to school early or would it in fact be good for her? what would you do or did you do?