With her side trailing 5-3 to Oxford University with three minutes remaining, she took a pass some 40 metres out and snaked her way towards the try line.
The defence could not stop her and the former Scotland under-20 player was the matchwinner, Cambridge holding on 8-5 to lift the trophy in the 33rd women’s Varsity Match.
Grant, the 21-year-old from Edinburgh, said: “We had been behind the whole game and we knew we had more to give.
“We had a team huddle with about five minutes to go and we said we wanted to go upfield and play on our terms. The winning move came off the back of that.
“I thought ‘this is our last chance’ and I just went for it. The white line was there and I just had to do my best to get over.”
Meanwhile, Scotland age grade cap Archie Smeaton and others with Scots’ connections – Chris Bell, Charlie McCallum and Dougal Russell – helped Cambridge complete a double by winning the 138th men’s Varsity Match 15-0 later in the day.
Fergus Jemphrey crossed the line either side of half-time, and scrum-half Bell added a further try for Cambridge, who included former Australia captain James Horwill and ex-South Africa lock Flip van der Merwe in their line-up.