The Ponzi-style scheme relied on upfront customer payments to cover debts, Portsmouth Trading Standards said.
Victims thought they were buying discounted holidays including honeymoons or once-in-a-lifetime trips to resorts in Barbados, the Maldives and elsewhere.
However, Simpson forged booking confirmations and bank statements to show payments had been made, prosecutors said.
In some cases, holidaymakers only discovered the problem after setting off and had to pay extra to rescue their trips.
Portsmouth City Council said it would try to recover money for customers through a proceeds of crime hearing in court.
The UK Civil Aviation Authority said Sphere Events displayed ABTA and ATOL logos despite having no affiliation with either travel protection organisation.
Lord Michael Bichard, chair of National Trading Standards, said: “Simpson’s actions took advantage of people who had saved hard for dream holidays, honeymoons and once-in-a-lifetime trips.
“She left some victims stranded abroad, facing significant emotional distress and, in some cases, tens of thousands of pounds out of pocket.
“As we approach the summer holiday season, we urge people to be cautious of deals that seem too good to be true, to check independent reviews and to report any concerns to Citizens Advice consumer service.”
