@Boddica2000
For once and for all it is completely and totally legal for her to post these pictures. No idea why people would pretend otherwise when a quick search will find the answer for you.
Tough to say for certain with the information provided, but this behavior may meet the threshold for harassment under UK law, which is a criminal offense rather than a civil matter.
The act of taking/publishing an image of someone in a public place isn't the issue, it's the intent behind doing so. For example, if it was done to deliberately cause alarm, distress, offence, hostility, to intimidate or degrade.
"A quick search" is not always the best way to understand something, especially the law, which is often deliberately broad in scope.
@simsbustinoutmimi
Yes, it’s illegal and would be considered harassment by police.
Possibly, possibly not. To qualify as harassment, the unwanted behavior usually has to have occurred more than once. If these pictures have been posted more than once, eg in another group or on the woman's own page, or she has repeated the accusations in the comments or via DM, that may qualify the behavior as harassment.
A single incident can sometimes be sufficient, but it would have to be extremely egregious and have a serious impact on the victim. I'm not sure whether this would clear that barrier or not.