Annette Grant/NBAE via Getty
A source tells PEOPLE that the Fatal Affair actress, 51, is focused on keeping 10-year-old son Kez Sunday stable amid the controversy.
"Nia's main focus right now is her son," the source says. "Her priority is making sure he's okay and staying on his normal routine."
Long and Udoka, 45, have been engaged since 2015. She is also mom to 21-year-old son Massai Dorsey II, from a previous relationship with actor Massai Dorsey.
The actress returned to Instagram on Tuesday — nearly two weeks after Udoka was suspended from his role as head coach of the Boston Celtics last month following an alleged affair with a female staff member.
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Randy Shropshire/WireImage Ime Udoka, Kez Udoka, Actress Nia Long and Massai Dorsey
"A tip for mental health," she wrote on Instagram. "Learn to distinguish who deserves an explanation, who deserves one answer, and who deserves absolutely nothing."
Following the news of Udoka's suspension in late September — after allegations he had an inappropriate relationship with a female franchise staffer, PEOPLE confirmed — Long issued a statement exclusively to PEOPLE.
"The outpouring of love and support from family, friends and the community during this difficult time means so much to me," Long said to PEOPLE. "I ask that my privacy be respected as I process the recent events. Above all, I am a mother and will continue to focus on my children."
Udoka spoke about the situation following the news of his suspension.
"I want to apologize to our players, fans, the entire Celtics organization, and my family for letting them down," Udoka wrote in a statement, which was obtained and shared online by ESPN's Malika Andrews.
"I am sorry for putting the team in this difficult situation, and I accept the team's decision," the statement continues. "Out of respect for everyone involved, I will have no further comment."