Her exit coincides with the departure of global marketing manager Zoe Maolmhaadhog, who had been at Mardev eight years.
The duo are among a number of departures thought to have been triggered by a group shake-up.
The business has been undergoing radical change since it bought and subsequently merged with DM2-Decisionmaker, a leading US data owner.
It is not known whether either has a job to go, although it is believed Manda will act as a consultant in the short-term. Maolmhaadhog is understood to be setting up her own photography business.
Manda started her career in direct marketing at Reed in 1995 after spells in the magazine industry and at Stiff Records in the early Eighties.
She has built a strong reputation in the industry, sitting on the board of Fedma as well as a chairing its list council. Manda has also been on the board of the Telephone Preference Service and on the DMA international working party.
During the past two years, she has divided her time between the UK office of Mardev in Sutton, Surrey, and the US office in Chicago.
Maolmhaadhog joined Mardev in 2003, after working in sales and marketing at technology firm Cartezia and packaging supply company Pira International.
Neither was available for comment as DecisionMarketing went to press.
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