Gareth Taylor’s side put our 3-0 first leg defeat to the Spanish champions behind us courtesy of a hard-fought win over the Royals, with Chloe Kelly’s 87th minute strike enough to maintain our tilt for the WSL title.
And Mewis believes that thrilling late triumph at the Academy Stadium has left a lasting impression which the entire team will take forward into Wednesday's clash.
"I think our win this weekend really brought us together," she declared.
“I think having a late game win like that where (Lauren) Hemp did something so sick, it really brings the group together when you know you can fight hard and pull something out.
“We know we have this other mountain to climb on Wednesday but to see that nobody gave up against Reading, I think that just demonstrates how resilient we are.
“It made me really excited to get to showcase that we have a lot more fight in us. The mood has been good and positive coming out of the game.
“Just seeing the way we continued to push, it was a little taste of how hungry we need to be going forward tomorrow.
“It is a sign we have it in us and are all ready to perform.
“Everyone has been staying after practice, everybody wants to keep working on things and keep getting better. It's a special group.”
On a personal note, Mewis revealed that she has prior experience of overcoming a significant deficit when she was playing back in her native United States.
And the midfielder believes the qualities she and her former teammates showed in that comeback are also plain to see in Gareth Taylor’s side.
She recalled: “It happened in a State Championship. We were down at half time and came back to win 5-3.
“My dad was the assistant coach of that game and I remember him saying at half time that the first thing you need to do is believe you can come back.
“This group has that. I am really optimistic. It is going to be hard.
“We really have to grind it out. We have what it takes to grind it out. We are pumped and fired up.”
As a key cog in the United States’ 2019 World Cup win, Mewis is of course no stranger to performing under pressure.
But while she is keen to make her mark on the game, the midfielder is equally confident that the rest of the squad will band together and step up to the occasion.
“I think something that is so special about this group is that everyone brings something that nobody else necessarily has.
“Everyone in the squad brings some experience or some personality trait that really contributes to the group as a whole.
"I can bring some of my experiences, some of my leadership from all of the past places and teams I have played for.
“Everybody has that and everybody will bring that and we’re really going to need everyone to bring their absolute best.
"It's a great opportunity for everyone to come together and really bring their best.”