Update: my mums did a retail swap, and changed color from black to white (obviously this wasn't the factor but thought I'd throw the extra details in), and low and behold, no longer do shots look like they come from an over-glorified webcam
Have you tried a fresh restore of your moms iPhone? Did you turn of syncing? Are all your apps updated? Did you try a hard reset, or drain the battery from 100% to 0 %? Disabling ad tracking also helps...chances are its just a software issue
The trend of unequal quality has always been around. There are many threads on photographers forums about whether or not a buyer received a good copy of a well-regarded lens.
Lens complaints include issues about contrast, color, sharpness, edge-to-edge sharpness, chroma, linear distortion, chromatic aberration, vignetting, bokeh, flare, and perhaps a couple others that haven't come to mind.