Ms Johnson replaces Simon Roche, from JP Morgan, who held the position for the previous two years.
She is only the second woman to be elected president in the branch’s 23 year history.
With 25 years’ experience in financial services, she joined the CISI in 2000 and has been with Charles Stanley since 2014.
Ms Johnson specialises in portfolios for private clients, as trusts, charities and self-invested personal pensions.
The CISI said Dorchester plays a key part of life for Abby and her family; her husband also works locally and both of their children attend Damers First School in Poundbury.
Ms Johnson is also involved with the school’s PTA as treasurer.
Commenting on her appointment, she said: “I am delighted to be taking on the role from Simon.
'Supported by an enthusiastic committee, we will continue to provide high quality CPD events in our area.
“Our involvement in other CISI projects is increasing, and includes an annual black tie charity dinner, projects in education and the more recent launch of the Young Professional Networks.
“We are actively seeking collaboration with other professional bodies within our region, so there is plenty to be getting on with; these are exciting times.”
Jim Winter, CISI head of UK business development, said: “We are extremely pleased to welcome Abby as president of our South Coast Committee and we would like to thank Simon Roche for his leadership during the last two years.
“With over 600 members the committee covers areas including Bournemouth, Dorchester, Portsmouth, Southampton and Salisbury.
“We look forward to supporting Abby in the year ahead.”