An angle is still an angle, even if you transform it with reflections, rotations or translations.
There's one case where the angle won't be an angle. If the transformation implies to make the angle equal to zero, then it would become a straight line.
However, in a general sense, it'll be an angle still.
Additionally, the relationship between the image and pre-image is that both angles are not congruent, since the image was rotated 90° clockwise.