she can apply for ILR when she has been in the UK 2yrs - (upto 28 days but before her visa expires)
so if she came to the uk 8th sept 2008
she will have been in the uk 2yrs on the 8th sept 2010
8th sept 2010 - 28 days is 11 aug 2010 is the earilest she can apply
and as she has a 27 month visa, which runs out 7th nov ,but that a weekend, so the latest is about 4th nov 2010
so she can apply from 11th aug upto 4th nov
but she must pass the life in uk test first.