It does look like a tension problem, but she should have tested her machine before starting the project.
I would talk to her about the quality of her work and request that she either make the repairs or discount the entire job since you are not satisfied. She should also understand that if you are not happy with her work making good on it would help settle differences between the both of you. This could make or break future business since most people will only go to somone that is highly recommended. If she discounds the job, learn from this mistake and ask, ask and ask questions when looking for another quilter. This time ask to see her work before putting your quilts in her hands.
Your MIL will love the quilt regardless so don't point out the problems you had since she may not even notice them.
Good luck and please keep us informed on how this matter was resolved. Hopefully you won't have the same problem next time.