Thinking on the matter for a moment, I figured that seeing the leprechaun at roughly normal human height would be a good method of comparing her to your average, run-of-the-mill woman. Taking a deep breath, I looked at the leprechaun and in an unnecessarily theatrical voice commanded her to grow until she was half a foot shorter than I was. For a moment, it seemed like nothing was happening. However, as I peered at the tiny lass I began to notice a very slow change. Progressing at a rate which to me seemed only marginally more hurried than grass growing, I could tell that the leprechaun was indeed getting taller. Whereas she had once been smaller than the palm of my hand, I now found her to be roughly the same size as that extremity, having progressed to such a state in about thirty seconds. Attempting to do the math in my head, I eventually figured that it would take something approaching half an hour for her to hit the correct height. Pointing this out to her and asking if the magic always worked this slowly, I was greeted by laughter and the suggestion that I should've been a bit more specific about how long it should take. Wondering out loud what might happen if I tried to hurry the growth along, my musing was greeted by a thoughtful look from my only marginally less minuscule guest.
"I don't exactly know, but I'm thinking that you shouldn't test it. Never know what effects mixing such magics will have," she said, and knowing that there was no harm in waiting for her to grow, I decided to carry her inside the house in order to get away from any potentially prying eyes.
Sitting in my hand and seeming quite content to be carried, the leprechaun started to make conversation as I walked into the house. Her line of thought mostly consisted of all of the possible uses of my newfound abilities, from turning critters and inanimate objects into people to all of the pranks I could play on those who got on my nerves. The latter bit was what really seemed to get her excited, and I got the distinct impression that she had no small love of general mischief. Heading through my house and into the bedroom, I gently set my guest down on the bed and noted that she seemed just a bit over a foot now, having racked up quite a bit of growth in the not-unsubstantial time it took me to calculate the rate of her magically induced development. Wondering what to do for the remainder of the time it would take her to grow, I spent a scant moment in thought before coming up with an idea.