ID you observe that Karin is very bright, yet the routine tasks which she mentions are generally physical and mundane. How about setting her tasks which demand that she uses her mental abilities.

For example you could set her a task which required her to prepare an evening's entertainment for you which centered around a particular style of dress - taking Oz's idea of

Use a jar and pick... so she won't know until just before you leave... Prim and proper? Slutty? Heels or boots? Nylons or bare? Short skirt or long with a slit.
and slightly turning it on its head, or you could choose a theme, or a piece of music or a picture which she has to develop it from.

Give her a week to work this out, with all details being kept completely hidden from you, I am sure that will raise both your levels of expectation.

Think about the evening in the same you would prepare for a major themed dinner party - so she would work out every element of the atmosphere, lighting levels, scents, music, food, a performance to entertain you, a selection of toys with suggestive creative ways, within the theme, of how you could use them on her... I am sure you get the idea.

cariad