You're right; some BMWs are made in Germany! However, the company also created stateside plants to meet the demand for certain models. The BMW 3 Series Touring, 4 Series Coupe, and M4 Coupe come from Munich, Germany. However, the BMW X3 and X3M through to the X6M and X7 are made in North America.
If the sequence begins with a “W”, or the second character is a “B”, your BMW was likely made in Germany. A VIN beginning with “5” and followed by “U” or “Y” indicates a vehicle made in the States. I hope that answers your and your sister’s questions!