Does she need the feed, or does she just want a suck? Can you get her sucking something else and see if she goes back to sleep with that? Sounds like she's not wanting a feed, she's just used to having a cuddle and a suck at that time, which is why she's not stimulating your let-down.

I could be way off the mark here, but I've heard that this is the last hurdle before sleeping through really begins so just thought I'd share.