Heidi Feek has a message for fans overstepping their boundary amid a family dispute with her father Rory Feek.

The singer-songwriter, who, along with her sister Hopie has made headlines in recent months for a disagreement with their dad over their younger sister’s care, shared a picture to her Instagram Stories on Tuesday, Oct. 15 that showed an alarming message she’d received in the mail.

“If u don’t like me, just unfollow me. Don’t mail this to my home like a psycho,” she wrote atop the photo. “Also a firekid fan would never…we all know who’s (sic) fan u are.”

The anonymous sender signed the note from “Your former Firekid follower,” referring to Feek’s musical project with husband Dillon Hodges.

The message appeared to be written on a postcard, and encouraged Feek, 38, to call her father Rory, 59, and “‘apologize’ for the chaos you created” in an “adult conversation,” while also shaming her.

Heidi and her singer-songwriter dad have been at odds over the care of his daughter Indiana, 10, as Rory has barred Heidi and her sister Hopie, 36, from contacting Indiana due, he says, to their differing worldviews.

Amid her fight to reopen a line of communication with Indiana, Heidi has claimed that the child is not safe, as Rory and his new wife Rebecca are raising her within Homestead Heritage, a faith-based community that Heidi claimed in an Instagram post has a “troubling history” relating to child safety — an allegation the group strenuously denies.

Heidi was sued by Homestead Heritage for defamation in September, but has said she will continue to speak out for the sake of her sister.

That same month, Rory wrote in a blog post that he’d driven two hours to meet with Heidi and Hopie at their home in Alabama with the hopes of hashing out their disagreement. He claimed that no one answered his knock at the door, so he left two bouquets of peace lily flowers on the doorstep and drove back home. He says he later received a text from Heidi that said she and her sister would only talk to Rory with a licensed therapist or attorney present.

Heidi later told PEOPLE that she wasn’t home when her dad dropped by, and she found the visit “intimidating,” as she’d set “really clear boundaries.”

“We have such a hard time communicating with him and feeling heard that we really don’t feel like it’s possible without a third party,” she said. “[Visiting] was never for us, because if he was trying to reach us, he would do it in the way that we’ve requested of him, or at least text us and say, ‘Hey, I’m coming.’”

Heidi and Hopie have taken legal action against their father in the fight for time with Indiana, though details of the filing remain confidential, as the child is a minor. Legal proceedings remain ongoing.