Marietjie holds the degrees B. Comm. (Law) (cum laude) and LLB (cum laude) from the University of Pretoria, and a LLM (Property Law) from WITS University. In her final year she was awarded the Grotius Penning by the Pretoria Bar Council for the best LLB student at UP.
She joined MacRobert Attorneys during 1990, was admitted as an attorney, notary and conveyancer in 1992 and was appointed as a director in 1996. She practised as conveyancer before moving into the fields of litigation, commercial agreements, mineral rights, property claims, trade marks, copyright law, competition law, credit control and financial recoveries.
She represented successful litigants in milestone cases in the Supreme Court of Appeal and in the Constitutional Court.