The hardest finger for me was the 4th finger, so a) just introduce that slowly.
b) I quit taking from one teacher because she was holding me back. Don’t be to down on your relative–she was probably a little nervous.
c) does she have any other musical experience? Start teaching her how to read notes if not; that will break up the periods at the harp and might make you both more relaxed when you’re on more familiar ground.
d) When I show my cousins how to play something, I try to make them use at least their index finger and their thumb. They feel more like they’re ‘really’ playing.
All suggestions! Good luck! Have fun!