As I said the chair is specially made so she has to cast a few floats on it to run for the day. Also while magic is mentally exausting at first, consider she has been practicing for more than 15 years already. A few floats every morning after sleep would be like washing your teeth every morning. SOmething routine for her. And yeah I made it partially magical partially technology because while magic can create ships that fly and such, those require pretty big engines and even with the advance in tech, I doubt they can make personal things as chairs float just yet. They may be able to make wheel ones that move but I doubt about flying/floating ones. This way she can both practice her magic and move around its a win win