To be quite honest, I don't care if she drops 10/30 or 11/6, but either of those two dates would be perfect.
She could handle 10/23 as well... I'm not sure how much Carrie's album will open with, but I expect a decline in sales whereas I think Rihanna's might stabilize/increase (just a wild guess).
And she needs to steer clear of 11/13, 11/20, and 11/27. Anytime in Dec is kinda late because she should take advantage of Black Friday.
So basically she has a two-week ideal window of opportunity (10/30-11/6), with 10/23 being the lesser but still viable option.