Lorelei is still alive!
Here is what Bruno Heller had to say when asked about Emmanuelle Chriqui reprising her role as Lorelei Martins for the season finale:
"It's not a flashback, a typo or a mystical thing, you'll have to work out what other alternatives are left. It's a surprise, and it's a good one."
I don't see how this could work though?