Verb conjugation of "demostrar" in Spanish

After a wonderful mountain breakfast with a hot chocolate drink one can enjoy the view by looking outside the window and seeing the white landscape, high mountains and the sun reflected in the white powder.
After placing my luggage there I decided to walk into town and rent a bike. The neighbor of the guest house stopped me on the street and asked me if I was Mike. She told me that she was Luisa.
She started to walk with us and one could observe that she had lost some of the naivity many children have, due to the fact that she started to be a sales person long before she reached twelve.