Teddi Mellencamp cheated on husband Edwin Arroyave with married horse trainer, heated confrontation ensued: source

Teddi Mellencamp allegedly cheated on her now-estranged husband, Edwin Arroyave, with a married friend, Page Six is told.

An insider with direct knowledge of the situation tells us Mellencamp, 43, allegedly stepped out on Arroyave, 47, several times with a longtime pal, whose then-wife was also a close friend, beginning in May.

Page Six can identify the man as Simon Schroeder, who is Mellencamp’s horse trainer, and the woman as Karli Postel. The Daily Mail was first report on their identities.

Schroeder and Postel, who share two children, did not comment when contacted by Page Six.

Our insider tells us Mellencamp and Schroeder were in Florida together for an equestrian event while Postel was in California in labor with their second child.

“Karli thought it was suspicious that her husband was in Florida when she was giving birth,” a source told the Daily Mail.

When Schroeder returned to Los Angeles, our insider tells us Postel allegedly discovered inappropriate text messages between him and the “Real Housewives of Beverly Hills” alum, which led to a heated public confrontation.

“They confessed. Teddi promised it would not happen again,” the Daily Mail’s source said, adding that “Karli didn’t tell Edwin when she found out” because “she was willing to give Simon another chance.”

However, the Daily Mail’s source said Postel learned last month that Schroeder and Mellencamp’s alleged sexual relationship not only continued but also became “emotional,” so she informed Arroyave.

Our insider tells us Mellencamp’s alleged entanglement with Schroeder is the reason for her divorce.

“She filed for divorce from Edwin so that he did not have the chance to file and get her for adultery,” the Daily Mail’s source said. “It has been alleged that the marriage ended because Edwin cheated on Teddi, but it is actually the other way around.”

Neither Mellencamp nor Arroyave commented when contacted by Page Six.

The former Bravolebrity filed for divorce on Nov. 1 and listed the date of separation as Oct. 20 — even though she and Arroyave packed on the PDA at a charity event four days later.

Mellencamp is seeking primary legal and physical custody of their three children — daughter Slate, 12, son Cruz, 10, and daughter Dove, 4 — with Arroyave having “reasonable and frequent” visitation.

In his response, the former Skyline Security CEO listed the date of separation as Nov. 1 and requested joint legal and physical custody of their kids.

Mellencamp announced on Nov. 2 that she was divorcing Arroyave after 13 years of marriage.

“After a great deal of care and consideration, I have made the difficult decision to file for divorce,” she wrote in a statement posted on Instagram. “My priority is my children and ensuring that every care is taken with their privacy and wellbeing throughout this new chapter.”

Mellencamp — the daughter of famed musician John Mellencamp — noted that “making a public statement” was “not something [she] wanted to do,” but she felt “being open, honest and vulnerable” would help “protect [her] family from undue speculation and rumors.”

Arroyave, for his part, has alluded to the split via his Instagram Story with a cryptic message about “dark days,” a selfie showing him and his brood heading to church and various Bible verses related to praying over one’s children.