Tell her to enjoy it and put some funky music on. Too many instructions will blow her mind.
Where will she sew later, if only with you then you can do some. My 4 and 10 year old nephews. Picked up using machine quickly after watching a demo showing me the machine. They also managed to sew straight lines and did go slow on their own. Only problem they had after breaking a needle couldn't get it out neither could I. My brother managed with the aid of pliers.
Both can hand sew as well. Just relax and enjoy both of you.