A good therapist won't take sides between you and your ex-husband. A good therapist will do more than just tolerate the parent. A good therapist will put the needs of your kids first -- not her own. This t doesn't seem like a good t, nor has she been for quite some time. Her disrespect seems harmful to the kids and you. You can't get unstuck unless things change. You've been trying for change for a while now. I'd confront her. She was wrong to be texting during your kids therapy time (heck, your kid even knows it was wrong). I wouldn't care if she got upset or defensive when being called out for not doing her job.

Good for you for cancelling with your t indefinitely (assuming it was the same one you were having trouble with a while ago)!!