I would keep it. Brother is a reliable brand and this machine will be fine for a beginner and is inexpensive enough so that later, if/when she wants a more sophisticated machine, she won't feel bad replacing this one. You're an experienced sewer and feel you've gone the "cheap" route but in a way, your MIL may be right. No one knows if the niece will actually LIKE learning to sew, and if not, why spend more on something that will just gather dust?