AUCKLAND, New Zealand -- American fans watching back home may have missed it: after Sophia Smith scored her second goal in the United States' win over Vietnam in their opener of the Women's World Cup, Smith made a "zip your lips" gesture.

The television cameras did not catch the celebration in full, but it was a gesture to honor former Stanford teammate Katie Meyer, who died by suicide last year, USWNT defender Naomi Girma said on Monday.

"We said if one of us scored -- probably her [Smith] -- then we'd do that," Girma said. "It's just another way of honoring her."

At the 2019 NCAA College Cup, Meyer made the title-winning save in a penalty shootout and then did the lip-zipping celebration, which went viral and was featured on SportsCenter. Smith and Girma were on that team.

In March 2022, Meyer died by suicide, and since then Girma and Smith have used their growing platforms on the USWNT to raise awareness about mental health.

"With a lot of players, us included, speaking out on mental health, we see this as an opportunity to shed light on a lot of things that are important to us," Girma said on Monday.

"That's been something that's been at the core of this team for so long and for us to come in now and carry on that legacy is something that's really important to us."

She added: "It's something that's really important to me and Soph."

In an interview with ESPN's SportsCenter released Monday, Girma said she wears tape with "KM" written in marker every game to honor her friend.

Meyer, a star player at collegiate level, has been a key figure during this World Cup for her former teammates.

Smith's second goal in the USWNT's win over Vietnam was originally ruled offside until a video review overturned the decision, and when the referee announced it was a goal, she did the celebration, but it wasn't widely broadcast.

"That was for Katie," Smith said afterward. "Nai and I talked about it before the game. We were like, 'What can we do for Katie?' It was pretty iconic what she did in the College Cup and we just want to honor her in every way."

Girma, Smith and other members of the national team announced last week that they have partnered with Common Goal -- a soccer-focused, pledged-based charitable project -- to launch a mental health initiative during this World Cup.