Duh, I should have read your other posts, before I did my last one...lol
I see you are feeding her a high quality food. I know that when I thought my two had dull fur..it was because I was trying out all different kinds of products. I've settled on "Bio groom" Fluffy Puppy and their Silk condtioner. I make sure to rinse out the fur really really well.
Are you growing her coat long?? I also noticed that when I cut down their fur...it gave the newer healthier fur a chance to come through. Now, I can get it long again.
I think the larger ones are better at tricks too..
As for the purse dogs....my two are 7 and 8 lbs and I can't imaging carrying them in a purse....it would be so heavy