for what purpose were they used?
No, but the photographs belong to the person who took them. She did consent to that and anyway you don't need consent to take photographs. If you did the press would be acting unlawfully almost all of the time.
Unless she specifically agreed on the basis that the negatives were hers there is no wrongdoing in use of them per se.
If she is 18 or over then indecent photographs don't apply.
To be wholly honest, if there is no nudity then probably revenge porn wouldn't apply either.
I suppose I haven't seen the photographs or the captions but they don't seem to amount to anything that would offend against the obscene publications act either.
Well, there may be but that doesn't amount to a criminal offence. Lovers breach trust all the time and that is a relationship issue.
I suppose she could seek an injunction but unless the images belong to her and not him I'm not sure it is the strongest application. He might well remove them if she threatens to though.
All the best.