(midnight Irish time).
Kelly, who was capped for the time against South Africa last week, scored on her debut to cement her spot as one of Ireland s back-up three-quarters.
In other changes to the team, who have a chance with victory to finish fifth in the final rankings, Highfield prop Marie Barrett makes way for Ulster s Gillian McAllister, Rosie Foley trades places with Geri Healy, while winger Nuala Ni Chaidhain comes in for Suzanne Fleming.
On the bench Clonakilty prop Laura Guest loses her place as Irish coach Philip Doyle has gone for an extra back, while there is no place either for replacement scrum-half Louise Beamish.
Scotland, despite a brave performance against New Zealand, which saw them trail 6-0 at half time, end up in fifth place, thanks to an inferior points difference to Canada and France. Ireland's win saw them climb the table to finish 8th - aided by Spain's shock win over Samoa.
Ireland beat Scotland just a week before their departure for the World Cup and if they win they could finish fifth in the final table - a remarkable feat considering their two early losses against France and the USA.
In a repeat of the last four in the 2002 tournament, defending champions New Zealand take on France, followed by England's encounter with hosts Canada in the semi-finals. If Ireland win tonight they will face the USA or Australia who square off after their game.
Ireland team to play Scotland:
F Coghlan, J Lonergan, G McAllister, C Mahon, R Foley, O Brennan, R Boyd, J Neville, T Rosser, J O'Sullivan, N Ni Chaidhain, G Davitt, L Cantwell, J Feighery, SJ Belton (c)
Replacements. Y Nolan, M Barrett, R Foley, E O'Sullivan, M Kelly, S Houston, S Fleming
IWRFU Press Officer