In the 1st and 2nd T20I, whether chasing or batting first, India managed less than 120 runs, which is below-par against a top team like England.
Mandhana reckons playing fearless cricket in the domestic circuit will take time because batters have the fear of getting out.
Chasing 112, England Women won by five wickets in the final over in Guwahati.
Brunt claimed 3/17 and Linsey Smith 2/11 to keep a check on India in Guwahati.
Mandhana also said she doesn't regret electing to bowl first in the first match, despite the bowlers giving away too many runs.
India lost all their T20Is in New Zealand and things seems to be heading towards a similar direction against England.
Goswami's new-ball partner Shikha Pandey has gained 12 spots to reach fifth position after also finishing with eight wickets against England.
Chasing 161, India women crumbled in their chase to finish on 119 for 6 to hand England women a 41-run win.
Tammy Beaumont struck her fourth half-century to guide England women to 160 for 4 against India in the first T20I.
The three-match India versus England T20I series kicks off in Guwahati on Monday.