No it's not birth control. It's used for estrogen replacement (usually menopause symptoms.) It's usually to use it in a 26 year old, but not unheard of. I would call the pharmacy and have them double check what the doctor wrote. Either the pharmacy or the doctor messed up (or your girlfriend isn't telling the story straight).
Do you know what "off-label" use means?I had her specifically go in for the birth control patch, so unless she somehow completely miscommunicated that fact to the physician, and since I am looking at the box on her desk as we speak, yeah either the pharmacist or doc made an error.