X and Y profile of a round object using a 45degree mirror (why is the Y profile smaller)

I’m trying to measure the X and Y profiles of a round object using a single camera. The camera has a direct view of the object in the X profile but sees the Y profile of the object as a reflection on a mirror mounted at 45 degrees. The problem is that the Y profile seen by the camera is smaller than the X profile of the object. Although the object is round. See the attached diagram, photo of the setup and a photo from the camera.

I would think that the reflection of the Y profile will be the same distance from the camera as the X profile and therefore have the same size. But it does not.

Why is the Y profile smaller than the X profile?
Or why is the Y profile (reflection) further away from the camera?

I did get the mirror from my wife’s makeup so it could be that the reflective coating is at a radius. But the glass itself seems flat.