The 18-year-old wing sprinted almost the full length of the field after picking off a stray pass as Scotland laid siege to the Irish line at Energia Park.
The home side had taken control of the contest in the early stages, hooker Cliodhna Moloney throwing a dummy before shaking off three opponents to score before Sene Naoupu also crossed to make it 13-0.
However, Moloney’s departure with a head injury after 27 minutes helped Scotland swing the momentum in their favour and Lisa Thomson’s try was converted on the stroke of half-time by Helen Nelson.
The visitors were pushing for the score which could have given them the lead in the 65th minute when Parsons intervened in memorable fashion and although Emma Wassell’s converted score made it a four-point deficit five minutes from time, Ireland held on despite Leah Lyons being shown a yellow card.
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