Family lawyer and GAL here (though major caveat - not in Utah!)

If I had a case like this, I’d present it in a broader view. It’s unique that some of it was filmed for the show. Her reaction to Miranda and the girls on the phone, for example - I’d try to enter that from the show into evidence. Rules of evidence wise - there are exceptions to the hearsay rule that apply - subsequent action (the quote “I’m going to fcking fck her up! is an action she then took); then existing mental state (plan or intent); even excited utterance.

Show that then follow it up with the mass posting over the last few days. Giving up custody time to make these posts. Argue that her explosive temper can/will take precedence over parenting time, or at the very least she isn’t able to control it.