Strokes for EPS Print Setup

Hello! My coworker and I have been having an issue since Friday when it comes to stroke sizing once exported as an EPS. One of our print vendors requires a magenta spot color stroke the same size as the artboard. When I went to export as an EPS to send to them, my coworker stated that the stroke was slightly bigger than the artboard size. When I opened up the same file, it did not show up on my end and was the same size as the artboard. When she saved a file and I opened it, the same thing happened - I saw the sizing difference but she couldnt. We believe this to be a bug but any help would be appreciateted as it is impacting the files when our vendor opens it to print!