Cowell was born in 1958, one of the daughters of Bob and Anne Cowell from Pulloxhill, Bedfordshire. Her introduction to motorsport came in 1973 at Long Eaton Stadium, a stock car racing venue in Nottinghamshire, when she took first place in a fancy dress car parade — dressing as a mermaid atop a car modified to resemble rocks, with driver Tony Allen portraying Neptune — earning what she later described as the first award she received in motorsport.
Cowell's competitive debut followed in 1974 in the junior ranks of mini-rod racing, a contact-heavy form of oval-track competition using modified Mini vehicles. By 1976 she had progressed to senior events, competing for the P.R.I. team; a programme from that year's Northampton Stadium meeting notes her recent debut three weeks prior at Oxford Stadium. In 1978, at the age of twenty, she claimed the British Mini-Rod Championship. Her mini-rod career culminated in 1981 when she won the British, European, and World Mini-Rod titles in the same year — a triple crown.
Following her mini-rod years, Cowell moved into closed-bodywork circuit racing. In 1982 she entered the Mini Se7en/Mini Miglia Winter/Southern Series, earning the Novices Award. She won the Lydden Hill Mini Seven championship in 1983 and finished second overall in the Mini Seven championship in 1984.
From 1985 she competed in the Production Saloon Championship. In 1987 she claimed the Class D title driving a Suzuki Swift GTi, recording multiple class victories including at Castle Combe. In 1988 she switched to a BMW M3 in Class B and achieved a class win at Castle Combe. She also contested the ESSO MG Metro Challenge in 1987, driving car number 18.
In 1987 Cowell made her debut at international level, sharing a Toyota Corolla GT with Geoff Kimber-Smith for the World Touring Car Championship round at Silverstone — the RAC Tourist Trophy — but the car retired.
Her BTCC campaign began in earnest in 1988. The season opened with the Donington 1 Hour Endurance race, where she and Kimber-Smith shared a Toyota Corolla GT entered by Alan Docking Racing; they won Class D, completing 42 laps. From the Brands Hatch round onwards she switched to a Ford Escort RS1600i in Class D, prepared by North Essex Motorsport. Her best individual result in the Escort was a second in class at Brands Hatch. She scored 17 points across the season, finishing 19th in the Drivers' Championship.
In 1989 she made a single BTCC appearance at Donington, again partnering Kimber-Smith in a Toyota Corolla GT under the Five Star Racing banner. The car suffered a misfire and retired after four laps.
In 1993 Cowell competed at the Willhire 24 Hours at Snetterton as part of an all-female crew alongside Clare Redgrave and Kirsten Kolby, driving a Honda Civic. The team finished fourth overall. She continued in the Production Saloon Championship in 1993 and 1994 driving a Peugeot 106, recording at least one second place at Silverstone, before retiring from competition at the end of 1994 due to sponsorship difficulties.
In 1990 Cowell married Peter Babbage, taking a year away from racing and using the time to establish a performance driving school. She resumed racing in 1991 as Barbara Babbage with a Suzuki Swift, achieving several top-ten finishes in the Production Saloon Championship. In 1994 she was awarded full membership of the BRDC, one of the first women to receive that honour. Following her retirement from racing she maintained a low public profile in motorsport.