Born and raised in Coatbridge, Margaret has spent most of her life living and working in Central Scotland. She trained as a teacher and taught in primary and special education schools in Lanarkshire. However, Margaret left the profession in order to study law, and later graduated from Strathclyde University with an LLB and Diploma in Law and Legal Practice.

Margaret is a former Justice of the Peace and Non-Executive Director of Hairmyres and Stonehouse NHS Trust. In 2003 she was elected as the Scottish Conservative list MSP for Central Scotland parliamentary region and from 2003 to 2007, was the Conservative Party's Justice Spokesperson. Margaret was then appointed as Convener of the parliament’s Equal Opportunities Committee a role which she held until 2011 after which Margaret was appointed as the Scottish Conservative Local Government Spokesperson. From 2013-16 she was reappointed as the party's Justice Spokesperson. 

In May 2016, Margaret was elected as Convener of the Scottish Parliament's Justice Committee and Deputy Convener of the Justice Sub-Committee on Policing. Margaret is also a member of the Commonwealth Parliamentary Association (CPA) Scotland Branch Executive Committee and sits on the Steering Group for the CPA Commonwealth Women Parliamentarian's British Isles and Mediterranean Region.

Margaret is involved with many different cross-party groups (CPG) in the parliament; she is currently convener of the CPG on Dyslexia and co-convener of the CPG on Taiwan.

Margaret is married and lives in Bothwell with her husband Henry and their two westies Jack and Jamie.