Born and raised in Edinburgh, McLachlan attended South Morningside Primary School and Boroughmuir High School.

Before transitioning to rugby, Rachel was a Scottish Judo Champion and a Sainsbury’s School Games Judo Champion. Her athletic abilities in judo laid a strong foundation for her subsequent success in rugby.

Rachel’s rugby journey began at Glasgow Caledonian University in 2017, where she pursued a physiotherapy degree. During her studies, she joined the university’s rugby team, and also played for West of Scotland RFC. Within a matter of months, Rachel was picked up by Scottish Rugby for the Performance Development Programme, which put her on a path for international honors.

Just 12 months after picking up the oval-shaped ball for the first time and making her debut for Scotland, playing against Italy on November 4 2018, having already earned represented Scotland Women’s Sevens just three months prior. Four weeks later, when Scotland played Canada at Scotstoun Stadium, McLachlan was in the starting XV.

Since then, McLachlan has gone on to feature across multiple representative competitions including the Six Nations, Commonwealth Games (for Team Scotland Sevens), WXV2 and of course, the 2021 Rugby World Cup.

Away from her international career, Rachel has played for PWR sides DMP Sharks and Sale Sharks. In 2024, she signed with French side Montpellier.