Two basic options. The first, extravagant and short-lived but memorable - an activity she wouldn't have thought to do herself normally so surprise trips (a lot of planning though!) or exciting adventures like flying or car racing or anything wonderful, preferably intense. The second, luxurious and long-lasting, a dress watch, dress bag, fabulous skirt - something high value that will last but will be used and loved and will remind them of you every time - don't dismiss jewellery entirely just yet, go for something that can be engraved, it makes a strong memory. I have done both for friends and they both worked. If she is adventurous get her something to keep, if she isn't get her something to remember - everyone else will buy for her dominant personality, but even adventurous girls like beautiful things and elegant girls like fun!