you are at peak potency right at this momment, I know this is confusing for a lot of people because they are reading bad literature and having people tell them when they like to harvest but the fact is that you are all opaque trichomes and it looks ripe for a sativa to me ...the guy at your grow shop is right, if you start seeing amber then it is degrading in this situation.
here is a quality article about the maturation of cannabis:
http://www.kindgreenbuds.com/marijuana-grow-guide/cannabis_maturation_harvesting.html
you need to understand fully the process that is happening on a scientific level, do not go by peoples little 'rules'...you need to look at the big picture also and not just at the trichomes, this plant is in my eyes clearly ready. yes it still has some 'hairs' sticking up...yes it still has some 'white hairs'...but the fact is you have demonstrated by your description of her maturation, your pictures, and examination of the trichomes that she has reached the Peak floral stage which is the ideal time for harvest, OFF WITH HER HEAD! (or wait 2 weeks for the hell of it)...either way you wont be disappointed - just chop it down when its convenient for you really, shes ready at anytime from now to the coming 2 or 3 weeks, you could even let her go 4 or 6 more weeks but lets be honest here, it really wont make that much of a difference in this type of scenario most people wouldnt likely be able to tell the difference if you harvested it now or 6 weeks from now.