The 25-year-old American defeated the French second-seed Nathalie Tauziat, 2-6 6-4 6-4, after two hours and six minutes of error-strewn tennis in a final that fell below expectations.
Earlier in the week, McGrath, ranked 53rd in the world, had beaten Natasha Zvereva of Belarus, the third seed, 6-1 6-0, in the third round and then the top seed Brenda Schultz-McCarthy, 3-6 6-3 6-4, in the semi-finals.
It was only the Swiss-based McGrath's third title on the WTA tour, having previously won tournaments at Oklahoma City and, more importantly, on grass at the pre-Wimbledon event at Eastbourne two years ago.
Tauziat, who won at Eastbourne last year, had her only chance of victory when she had three break points for 4-2 in the second set. However, McGrath held on, broke in the next game and served out the set at 6-4.
Five successive breaks in the final set, when both had trouble putting their first serves in and therefore could not get in to the net, left McGrath leading 5-4, and she went to match point with a service winner before Tauziat struck a backhand into the net to end the contest.Reuse content