ceiling and window alignment problem

i have just put a very nice pelmet on the window in the office/study room and when standing back to admire my handywork, it all just didn't look level, something looked amiss. I get the level out in a panic and window (which i put in) and pelmet are spot on but the ceiling slopes upwards slightly.

SWMBO claims she can't see anything but i can. i measured the window to the ceiling and there is a 15mm difference over the 1300mm of the window width. Is there anyway i can hide this or at least make it look less noticable?:C

Maybe you could raise one end of the pelmet 7mm, just to make the difference less obvious???
TM

gave that some thought TM but i have venetian blinds and that throws it out as well. i will try with raising the pelmet 7-10mm on one end and the blind maybe 3-5mm and see how that goes.