The bible says Make a joyful noise. Everyone is not blessed with the gift to sing harmonously or even pleasantly, but she does have a right to make a joyful noise to her God It may hurt your ears, but pray for her do not laugh at her. she is a child of the King, just as everyone else. She has right to praise Him. I agree music should be in a manner to usher; however, sometimes, the lyrics themselves are more powerful than the key, the tone, the pitch and THE INSTRUMENTS.
Ease up people. She may not have voice like others, but she is willing to give back to God what He has given her and I am sure that where it might hurt your ears. It is like sweet, sweet music to HIS.