Despite no pressure from any City player, the Swedish global seemed caught in two minds as Demi Stokes floated a cross in from the left and inadvertedly diverted it past her own keeper and just inside the post. After Ramona Bachmann squared the ball to Fran Kirby, the Chelsea forward was in on goal, but the City 'keeper stood her ground before blocking Kirby's shot with her foot.
But Eriksson's uncharacteristic late moment of madness sent City to Wembley.
Nick Cushing's side, who lifted the trophy in 2017, will now hope to add to their Women's League Cup triumph earlier this season.
The Blues then hit the woodwork through Kirby's header from Cuthbert's flighted free kick.
But it was Eriksson's own goal in the first minute of injury time that eventually proved the difference, denying Chelsea a place in what would have been their fifth final.
"Knowing the way that we work at Manchester City, we'll all just concentrate on our next game and make sure we win that one". We were confident throughout. We didn't get out of second gear most of the time. She played the ball out wide Stokes, who's cross curled towards the Chelsea back post.
Tanya Oxtoby's side are now fifth in the WSL standings with two games to play and Oxtoby's side will be looking to finish their season with a flourish when they welcome the Hammers to the SGS College Stoke Gifford Stadium. I will remind her of how wonderful she's been this year. "It was an unfortunate goal to concede for them but we're at Wembley and that's the number one thing". It's a cruel way for the game to end.
"We all know that [winning every trophy] is going to be incredibly hard", he said. It was an even game.
It would mean everything, it's a massive journey, for us to be drawing against West Ham in the semi-final we couldn't have got more lucky I guess.