Mackenzie Shirilla's Prison Selfies Spark Outrage From Dominic Russo's Family

12:23 PM PT -- Christine Russo joined us today on "TMZ Live" Wednesday, where she explained that Mackenzie's behavior is making a mockery out of their family's tragedy.

Mackenzie Shirilla is posting glammed-up prison selfies on Instagram ... but Dominic Russo's sister tells TMZ all she sees is a convicted killer soaking up attention online.

Mackenzie's new prison selfie and a message saying she's "trying to do better every day and holding on to hope" has Christine Russo demanding prison officials investigate whether she's improperly accessing social media behind bars.

Christine tells TMZ ... "As Dominic Russo's sister, it is heartbreaking to see someone convicted in connection with my brother's death appear to have a social media presence while our family is suffering every day. While my brother is buried, seeing her post selfies, full face of makeup, and bragging how she is famous is painful and, to me, completely inconsistent with remorse."

Dominic's sister goes on to encourage anyone with similar concerns to contact the Ohio State Reformatory for Women and "respectfully ask the warden to investigate" whether any prison rules regarding electronic devices or social media are being violated.

Christine adds ... "In my opinion, if these reports are accurate, they should be taken seriously, and I don't understand why someone with a disciplinary history would continue to have privileges that allow this to happen. Victims' families should not have to watch the person responsible for their loved one's death seek online attention while they continue to live with unimaginable loss."

She also urges people to report influencers who allow Mackenzie to appear in their livestreams, telling us ... "These vile internet trolls harass and threaten myself, my children and my family and should be stopped."

As TMZ previously reported, a new prison photo of Mackenzie recently appeared on IG after the Ohio Supreme Court declined to hear her appeal, leaving her convictions and concurrent 15-years-to-life sentences untouched. The post said she's "trying to do better every day" and asked followers to keep supporting her.

Mackenzie was convicted of 12 felony charges including murder, aggravated vehicular homicide, and felonious assault after prosecutors argued she intentionally drove her car into a brick wall at around 100 MPH in 2022 ... killing Dominic and his friend, Davion Flanagan.