NEW YORK -- After Coco Gauff sealed her rousing three-set victory over Laura Siegemund in the first round of the US Open, former President Barack Obama and former first lady Michelle Obama were waiting in the wings to greet her. 

"I've met Mrs. Obama before," Gauff told reporters. "They told me it was just her initially. Then Mr. Obama was there in the room, too. I haven't soaked it in because I literally just walked in here. 

"I think I'm going to never forget that moment for the rest of my life. I went from being really upset after a win to being really happy."

Gauff digs deep to notch comeback win over Siegemund

It was the coda on a rollercoaster night for the 19-year-old American, whose poise and maturity was on display as she earned her first night-session win on Arthur Ashe Stadium. En route to her come-from-behind win, Gauff engaged in a passionate back-and-forth with chair umpire Marijana Veljovic about the time Siegemund was taking between points. 

"It doesn't matter if it's a long game," Gauff told reporters afterward, referring to the flexible application of the time-violation rule. "Endurance is part of tennis. If I'm going in the gym four hours and I'm running tracks and doing cardio, that's to prepare me for these long moments, so she should be as prepared."

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Gauff said she bottled up her frustration for most of the match, but when Siegemund held up her serve in the third set, she finally had enough.

"I really don't like confrontation all that much," Gauff said. "I was thinking about it the whole match. I wasn't sure if I was in the right or not until it happened multiple times. Then I was like, Okay, I know I'm in the right.

"I think it just reached a point where I was just really frustrated. For me, I try my best not to let my emotions take over myself. I wanted to express my frustration, but also being censored. I didn't want any bombs to fly or anything. I was trying to best communicate how I was feeling to the referee."

Gauff says she wrestled with the idea of saying something to the umpire sooner, but she kept catching herself.

"I didn't want to come off as a complainer," Gauff said. "Sometimes in your head, also being in the public [eye], you think about all these actions that don't have to do with tennis, like talking with the ref, throwing the racquet, banging the racquet. It's stuff that I think about, honestly.

"It is something that I think about, my maturity level, because I know it's something that people look at a lot. I know you do one wrong move, people are going to call you all types of names and tear you down."

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Ultimately, Gauff got her point across and acquitted herself well in the moment. After rewatching the exchange during her post-match ice bath, Gauff says she has no regrets.

"I think as long as you approach a person with respect, then everything should be fine," she said. "I didn't approach her with any type of disrespect. I was being respectful. 

"That's what I was taught, to do things in a respectful way. Only when you're disrespected, then you're allowed to get disrespectful. I don't think the ref disrespected me, so I came up to her in a respectful way." 

And, as Gauff found out later, the Obamas agreed.

"They gave me some good advice," Gauff said. "They just told me how I handle myself in these situations, she said it's good to speak up for myself. I think she was happy that I spoke up for myself today."