I'm sure you'll get some good sound advice soon... but all i can think of is that she's having a bit of a growth spurt during those evening hours (And at the same time i'm thinking to myself I WISH as my 8 month old has possibly managed 2 or 3 8hr blocks in her life.... ) I'd also say that yes, she's probably becoming a bit more efficient at feeding now and your supply may be more than she needs and is yet to settle properly to suit her appitite.

Try not to stress too much your little one will surely not starve herself and if she wasn't happy with what she's getting she'd be well and truely letting you know