The Stormont club beat Muckamore by two runs on that occasion but suffered defeats to Lurgan (2018) and Waringstown (2020) either side of their maiden success.
They return to The Lawn to take on North Down – who are making their first final appearance since defeat to Lurgan in the 2017 decider – and are on the cusp of a league and cup double.
Rachael Thomas’ side suffered their first Premier League defeat of the season earlier this week but they remain eight points clear at the top and are determined to add another two trophies to their collection.
It has been a year of progress for CSNI and Thomas is looking to round it off on a winning note.
“We are really pleased with how the season has gone for us so far, with the hard work we have put in during training paying off during the matches we have played,” she said.
“We have grown in strength this year and it has been great to see lots of our younger players taking on key roles.
“We are all really excited to play in the final on Sunday and ultimately, we are looking to enjoy ourselves and treat this day as a reward for our hard work this season.”
North Down booked their spot in the final with an impressive 1-run victory over Lurgan, who had earlier knocked out reigning champions Waringstown.
Amy Benson scored 80* to help her side set a winning total and she will once have a key role to play alongside captain Staci Maxwell.
These two sides met in the league last month with CSNI winning by just three runs, giving an early indication of how tight the decider could be.
“CSNI are, in my opinion, the most well-rounded team in the NCU and have been for a few years now,” said Maxwell. “They have depth in batting and several different bowling options.
“We know that it won’t be an easy game but are excited for Sunday. We will be hoping that history repeats itself and we can get the win.”