Your quilter has absolutely no excuse, don't use her again.
Tension problems can be a real problem for quilters, the fabric color your quilting, the type of thread your using, and of course the top and bottom tension settings themselves.
I have a handout on tension that we use to give to our longarm customers, we siold Kenquilt LA machines, that I would be willing to post if it would help.
I don't have the means to convert it to a PDF, its in Word 2008, and I have been told that that is the perferable doc type to post on this forum. So if acceptable to the forum, just email me privately, and I'll send it to you.
Lanny