I agree with other posters. Let her know that you weren't happy with her quilting and let the shop know that they did you a huge disservice recommending someone who had JUST GOTTEN their long arm! Perhaps she previously took in hand quilting and they don't know that her long arm skills are poor. Either way, they shouldn't be recommending someone who is obviously not yet up to professional standards.
It isn't ruined however. It's a dorm quilt. Wash it, dry it, and your niece will be thrilled. The batting will nicely wrinkle it and the errors will simply fade away. Only quilters notice the errors, believe me.
I belong to another board and every time someone there gets a long arm, I send that person several of my quilt tops to practice on. These are quilt tops that I didn't really invest a lot of time on. Usually scraps. Sometimes the results are absolutely fabulous. Sometimes not so much. However, the recipients have all loved their quilts and I get a quilt done for very little money while a new long-armer (is that a word?) gets a chance to practice on a 'real' quilt.