I cluster feed my two in the evening as well, and did with Maya. The different breastmilk think doesn't hold true for the twins as they are having the milk I expressed in the morning at night but it might have done with Maya. I feed them at 4pm, then 5.30 (but only a half feed) then 7pm and then they go to sleep. Ultimately I'd like to get a bath in there like I used to with Maya but atm we bath them in the morning when the nanny is here coz it's easier with an extra pair of hands.
The rest of the time between 4-7 we just try to 'get thru' the witching hour - sometimes one or both of them catnap in the bouncer or on the floor, or else Willie and I just lug them around the house. Maya was exactly the same - wouldn't settle in her cot at that time of day and wanted to be carried everywhere.
It is a bit of a pain in the butt that it has to be at that time of day tho - right when I am trying to get Maya fed and bathed etc.
Will Ella doze if you carry her or rock her? I know it's a 'bad' habit as such but my girls all seem to have figured out that it only happens at that time of day, the rest of the time it's straight into the cot, and that little 15-20 min catnap is enough to get them thru without getting overtired.
I like Peace's expressing idea too, means you could get DH to feed Ella sometimes so you can take a turn at cooking (if you WANT to

) and it's less tiring for her than breastfeeding.