Matthews first struck a well-played 52 off 35 balls to help the Warriors post 156-6 off their 20 overs after the Barmy Army won the toss and elected to field first.
She wasn’t the star of the day with the bat, however, as South African Mignon Du Preez shone with an excellent 75 not out off 54 balls including six fours and three sixes.
Dottin took 1-11 off two overs for the Barmy Army before leaving the field with a slight injury.
Matthews then returned to pick up 2-3 off three overs to combine with Sri Lanka’s Udeshika Prabodhani (2-17 off two overs) and restrict Barmy Army Women to 102-8 off their 20 overs.
Pakistanis Fatima Sana (34) and Rumana Ahmed (26 not out) were the top scorers for the Barmy Army Women.
Warriors Women finish their tournament with one win from five games, while the Barmy Army Women will now move on to the semi-finals alongside Spirit Women, Tornadoes Women and Falcons Women.
With the three-match contest tied at 1-1, the hosts were bowled out for a disappointing 116 after being invited to bat first in the decider at Derby.
They never got to grips with Sri Lanka’s array of slower bowlers, with Chamari Athapaththu taking three for 21 and Udeshika Prabodhani and Kavisha Dilhari both claiming two wickets apiece.
Maia Bouchier top scored with 23 while Danielle Gibson added 21 late as England were skittled in the 19th over.
The innings could not have got off to a worse start as Danni Wyatt planted a gentle wide delivery from Inoshi Fernando straight to cover.
The Sri Lankans were celebrating again at the end of the second over when a calamitous mix-up between Bouchier and Alice Capsey saw both batters at the same end, with the latter ran out.
Bouchier and captain Heather Knight did some repair work, sharing a 30-run stand in four overs, but that came to an end when Bouchier holed out to long-on.
Knight (18) and Amy Jones (20) soon followed as England slipped to 72 for five in the 11th over and it looked like they would struggle to get to 100.
But Gibson hit three fours in her 15-ball innings to get them to three figures before a flurry of late wickets saw them fail to see out their overs.
