Danielle Rowe got the only goal of the game when she scored on 18 minutes.
But it proved a hard-fought game throughout with the Blues failing to find their top fluent form.
Boss Sadler knows they need to improve on that.
'We wanted to show him a bit of love' - Portsmouth-based Spurs fans' terrific gesture to ensure Dane Scarlett feels at home on the south-coast
League One latest: Portsmouth linked duo set for Oxford United and Lincoln moves, Southampton prospect joins Blues rivals as Ipswich land former Blackpool and Derby veteran
Denver Hume: Portsmouth's expensive forgotten man and why former Sunderland defender really could be one for the future
Danny Cowley offers update on Portsmouth's forgotten man and ex-Sunderland full-back sidelined for five months
The most expensive estimated League One combined XI - including two Portsmouth, four Barnsley, one Oxford United and two Derby aces
He is expecting better when they travel to Moneyfields in the Portsmouth & District FA Cup on Sunday (2pm).
He said: ‘We’re delighted we are through to the final of the Hampshire Cup again. We got a win and a clean sheet but the manner in which we won the game was disappointing.
‘There was no real tempo to our play.
‘We looked sloppy with the ball. Overall it was disappointing. We pride ourselves on performance and we have got to work on elements of that.
‘It was professional and we are happy to be through, we saw the game out.
‘We defended well and got a clean sheet. Jaime Rowlands made some great saves, especially considering her injury in the warm up. Massive credit to her
‘The focus is now on training and Moneyfields. We need to see a reaction against Moneyfields.
‘I want a return to the style, tempo and swagger we played with against Watford in the previous match before the cup tie. We have got to be better.’
Having beaten Saints Pompey will face Southampton Women in the final.
Sadler’s team are in the final for the 11th time in a row and will start as favourites.
But they will have to be on their game against a side who beat Warsash Wasps 11-0 in their semi-final.
It will be the third time in succession in the competition Pompey have faced a team from Southampton.
They will be hoping to complete the hat-trick of wins against them and retain the trophy.
The Blues boss added: ‘We have got be happy we are into a final.
‘It is a cup that is prestigious to us. We have had our name on it several times and we all want to retain it.’