Manchester City forward Hemp, 24, last played for England in the 2-1 friendly victory over South Africa in October.
However, she is yet to play 90 minutes this year and Wiegman admits that is a concern.
“Yes, of course it is. But we still have two months – almost. We want to keep building and see what she is able to do,” said the England manager.
“She has to perform at her highest level too but she has shown so many things before her injury that she has built some credit.”
City captain Greenwood, 31, has missed England’s last four matches but started November’s 0-0 draw with the United States and came on as a substitute in the 4-3 defeat against Germany in October before her injury.
Both players – who were part of the Euro 2022 squad – started City’s final two league games of the season having returned from injury in April.
Bayern Munich midfielder Stanway, 26, has not yet returned for her club but Wiegman is keen to give her more time on the training ground.
“She still needs to build. Georgia is in training. What we know is she can come into camp and continue building with us,” added Wiegman.
“Hopefully towards the Euros she can be healthy and can handle the training loads to recover from it.
“She has to be performing at the highest level – at her highest level – to compete for the position [in the Euros squad] just like everyone else.”
Chelsea forward Lauren James is still not selected as she recovers from the hamstring injury that forced her to miss the end of the WSL campaign.
England’s defence of their European title kicks off in seven weeks’ time with their opening match against France on 5 July.
Wiegman has previously expressed concern at the lack of game time for some of her returning stars, including Hemp, Stanway and Greenwood.
Elsewhere, Tottenham Hotspur’s Ella Morris has been called up from the Under-23s squad for the first time, alongside Aston Villa’s Missy Bo Kearns, who is recalled.
Striker Michelle Agyemang, who spent this season on loan at Brighton from Arsenal, retains her place in the squad after scoring a stunning goal 41 seconds into her debut in a 3-2 defeat by Belgium in April.
Aston Villa defender Lucy Parker, Manchester United centre-back Millie Turner and Brighton midfielder Maisie Symonds miss out.
