The neighbor, known only as Sonia B because of tribunal regulations, says she suffered from noise pollution caused by Martin's practice sessions, which last eight hours each day, five days a week, between 2003 and 2007.
During the five years that Martin, now 27, was studying at a music college, Sonia B lived above Martin in the north-eastern town of Puigcerdà, and says Martin's constant playing caused her trouble sleeping and led to nervousness, anxiety and panic attacks.
Sonia B also told the court that she eventually had to move out of her house and now hates pianos.
Martin has denied playing at home as often as the complainant says she did and said she took regular piano classes in other towns.
The trial is expected to come to an end on Friday.