India, stunned hosts England with a 35-run victory, also made it two wins from two as they overpowered the West Indies by seven wickets at Taunton on Thursday.
Opener Smriti Mandhana got to three figures with an unbeaten 106 following her 90 against England.
She added 108 runs for the third wicket with captain Mithali Raj (46) after India were in trouble at 33 for two chasing a modest 184.
“Smriti played well for her hundred, it was a crucial innings she played,” said Raj.
India´s spinners made life so tough for the West Indies that even the usually dynamic Deandra Dottin — holder of the fastest century in women´s T20Is — could manage a mere seven off 48 balls.
The West Indies slumped to 91 for six before some late-order hitting boosted the total.
“We didn´t get the batting right in the middle,” admitted West Indies captain Stafanie (attn eds: correct) Taylor. “We have the batters to do it but I think it´s up to the batters to take more responsibility in their actions.”
All the eight teams involved play each other once, with the top four contesting the semi-finals.
The final takes place at Lord´s on July 23.