She goes on to explain that while she was chatting to her friend Monica at the restaurant, she noticed that she was staring at something behind her and making a funny face.
"I stopped. 'What's going on?' After a few seconds [Monica] said 'That guy just put something in her drink'.
"They had a bottle of wine they were splitting. It seemed like a first or second or third date. "After a few 'Oh god. What do we do's, I got up to find her in the bathroom to tell her. Warn her. Tell her to get up and leave this creep. Make him drink it. Something."
After waiting at the sinks in the bathrooms, Sonia approached the woman in question.
"Hey! Um, this is kind of weird, but, uh, we saw the guy you were with put something in your drink," she said.
" ... My girlfriend said she saw him put something in your drink and we had to say something. Woman to woman ... you know."
She went on to ask the woman how well she knew her dining companion.
"I was expecting to hear 'We just met,' but I got: 'He's one of my best friends'."
It turns out that the woman had known the man for a year and a half and they worked together.
"When I got back to the table, Marla was talking to the server about what happened. Seeing if he or the manager could do anything."
Monica also spoke more about what she actually saw:
"He pulled her glass toward him, kind of awkwardly, then he took out a little black vial. He opened it up and dropped something in. Then he tried to play it cool, like checking his phone and hiding the vial in his hand and then trying to bring it back down slyly."
At this point the restaurant's manager approached the pair's table and offered her a glass of sparkling water. He then stopped by Sonia's table to say he couldn't do much at this point because he hadn't actually witnessed the incident, but he had alerted security.
"The poor woman had to sit through 40 more minutes, sitting across from 'one of her best friends' knowing that he was trying to drug her," Sonia continues in the Facebook post.
"Marla noticed him several times chinking his glass to hers to get her to drink. She played it cool. Mostly, I believed, just stunned. The staff wanted to jump in and dump the glass, dump him, do something! I was going through fantasies of walking up and demanding he drink the tainted glass of wine."
Eventually the pair finished their dinner, and there was a "delay" in getting their bill (the restaurant manager told the man there was a problem with the restaurant's computer). That's when the police arrived.
"They say 'Come with us' and he doesn't protest. Doesn't ask why. Doesn't seem surprised," writes Sonia.
"The head of security came by and said that because we notified them immediately, they were able to go back and review the footage from the security camera.
"They got him on tape. They had proof of him drugging this girl. They took the glass away as evidence. They kept us for statements."
They then asked the woman, who was "in shock" if she had a ride home. She said that her car was at the man's place and they had caught a cab to the restaurant together, a move that "must have been part of his plan".
The women were then approached by other people in the restaurant, who congratulated them for speaking up. Many of the people had their own tales of drink-spiking.
Sonia also praised the restaurant's managers, who handled the situation quickly and discreetly. "We are well aware how many people would not have taken what we said seriously. Not taken action. Said their hands were tied.
"So thank you, everyone at Fig and Fairmont in Santa Monica for keeping this guy from harming someone.
"And thank you in advance to everyone who sees this and shares this and reminds each other that yes, you SHOULD say something. Even if it's awkward or weird or just uncertain if anything can be done.
"Know that YOU did something. And that it helped."
