"Amber's trying to get things together in her life and she wasn't able to attend," a source told Us Weekly. "She's dealing with the situation and her most important thing is her family."
The reality star was arrested for domestic battery on July 5 after she was involved in an altercation with her boyfriend, Andrew Glennon. Portwood was holding a machete at the time of their argument while Glennon was holding their 14-month-old son, James.
"[Amber] struck the machete at and into a door, while Andrew Glennon was standing directly on the other side of the door, that created a substantial risk of bodily injury to Andrew Glennon," a document read.
The reality star was bailed out of jail the next day and was charged with two felonies and one misdemeanor. A few days following their disagreement, she was served with a no-contact order in court.
Her aggression towards him wasn't at random. According to a source close to the couple, they were having issues that lead up to the heated debate.
"There were things going on between her and Andrew that led to this," the insider said.
In the meantime, the rest of the cast which includes Maci Bookout, Catelynn Lowell and Cheyenne Floyd traveled to New York City for the reunion taping. Portwood's ex-fiancé, Gary Shirley, was there as well.
"Gary was asked about the situation and he was very diplomatic," a source said. "They have a nice relationship now."
Portwood and Shirley share a daughter together, Leah, 10.
Portwood has starred on Teen Mom OG since 2009, which was a follow up to 16 and Pregnant. During Season 8, the mom of two opened up about her struggles over the last several years with her mental health and where she's at in life as a woman now. She admitted to handling heated situations differently than she used to, in a more calm and reserved fashion.
Back in May, Portwood opened up to the outlet by reflecting on the last decade of being on the show, saying, "Just go for the ride because it's going to be crazy! I don't think I would have listened, but [I'd say], 'You're going to learn a lot of lessons and you're going to receive a lot of love for it. You're going to help a lot of people.' I think in the end that makes it 10 times better to show everybody all of my flaws."
Following her arrest, she's now on "thin ice" with MTV on whether they'll keep her or fire her. Teen Mom 2 star Jenelle Evans was recently fired by the network after her husband David Eason killed her dog.