I don't know any media outlet that does an investigation and then phones up the subject to say "all clear, carry on". Unless m'learned friends are involved, or unless the subject phones them to ask what happened to the story. If JM is claiming that Private Eye did an investigation into her affairs and didn't find anything, and then phoned her to tell her that her reputation was clear and they wouldn't be doing a story, she's lying.
Private Eye has some very determined and skilled investigative reporters, who have done deep dives into major stories like the shell companies based overseas that own a lot of property in the UK, and the Royal Mail audits that mistakenly blamed errors on postmasters and refused to consider evidence that cleared the postmasters. I honestly don't think that an investigative team that thorough could look at JM's dealings and *not* find something suspicious.