The reality stars were both at Sur on Tuesday night for a charity fundraiser.
Madix, 38, and Sandoval, 40, were both in attendance at Lisa Vanderpump's chairty fundraiser event -- held at her restaurant, Sur, on Tuesday -- where Vanderpump Rules cameras were reportedly rolling amid production on season 11.
However, despite both showing up to support the charity event -- which raised money for Maui Wildfire Relief -- Madix and Sandoval did not actually seem to converse, and didn't appear together in any photos at the event.
Madix stunned in an all-black ensemble for the party, and reportedly arrived with a male friend. She was all smiles as she spent time with some of her co-stars, including Scheana Shay, Katie Maloney and Lala Kent.
Sandoval, meanwhile, spent some time behind the bar with friend and business partner Tom Schwartz.
Sandoval rocked a gray-and-orange striped tank top, a black cardigan and black jeans, and appeared to enjoy the evening with his co-stars.
"Tom and Ariana haven’t filmed one-on-one and she’s telling her friends she won’t," the source said. "She’s made it clear she doesn’t want to film with Tom and is in a good place mentally, and filming with him will only cause disruption."
The source added that Madix is standing firm on the rule and is not participating in group activities with the cast, as they involve her ex.
Although, Tuesday's outing suggests it's possible she bent that one rule to support the Maui Wildfires Relief charity.
"Ariana has also skipped group things, like the recent trip, to avoid Tom," the source said at the time. "They ended up filming her and Katie looking for new hires for their sandwich shop."
In early March, Madix and Sandoval announced the end of their relationship after being together since 2013 when she first joined the show. It wasn't long before news broke that Sandoval cheating on Madix with their co-star, Leviss, is what truly derailed the relationship. And, as it turns out, this was just the tip of the iceberg.
Filming for season 11 of the popular Bravo reality television series began this month, shortly after the explosive season 10 reunion aired, where the cast and Madix collectively spoke about Scandoval.
When it comes to Leviss, she has yet to been seen filming, as she is still in negotiations.
However, Leviss did speak out for the first time in an interview with Bethenny Frankel that was released Wednesday morning. ET has learned that Leviss' interview with Frankel is three parts. Part two will be released on Thursday, Aug. 17, and part three will debut on Friday, Aug. 18. The entire interview and video will then be released on YouTube on either Friday or Saturday. Leviss will be addressing the many rumors and misconceptions surrounding her time on Vanderpump Rules.