I sympathise with you.
Everyday I see numerous illegal plates and the police never seem to do anything about it, so your daughter was probably caught by a rookie cop with some time on his/her hands.
I do object to a lot of personalised plates where the spacing is incorrect. To my mind they should be pulled over and suffer the inconvenience of being held up for a few minutes, then given a FPN.
The law on letter spacing and font is quite clear. The problem is that people buy show plates and keep them on all the time.
From what I understand, having had to get a new plate myself last year, all plates should have the BS Kitemark and the name and telephone number of the supplier on them. I may be wrong, but I believe this is the case.