Her post will be partly filled by Flagship account manager Suzie Pagan.
Bolitho formerly worked at Voca (previously Bacs) as head of marketing before joining Flagship last year.
Flagship also saw the departure of account manager Simon Walsh this month. He has taken a corporate account director role within Good Relations Corporate.
SEPARATELY... Flagship last week hired Virginia Webb as head of its Travel and Leisure Division.
She joined from BGB Communications, where she was an associate director.