AITA - I told my ex to stop bringing his new GF to our child's therapy sessions.

I (30F) have a son (8M) with my ex (29M) "Keith". Since our divorce, my son has been in therapy. <br><br>The sessions are a mixture of individual counseling, and family counseling. Keith is also in therapy with his own therapist. The first session, Keith's new GF "Jess" (28F) tagged along. The therapist asked if she could stay, and Keith said yes, and I didn't fight it since I figured she was there to give emotional support, and I didn't want to seem like the bad person. <br><br>The next session, she tagged along again. I told the therapist that I'm not comfortable with her staying. Therapist told Keith that it was fine, and he could bring her back after the session was done. <br><br>Keith got very upset. He told me that I was being mean and petty. He said that Jess isn't doing anything wrong, and has done nothing but help our son, and be kind to him. He said that she has the right to hear anything that our son has to say since she is in his life. <br><br>I told him that her being in my son's life is temporary, and I don't want her there at the therapy sessions. He got mad, and told me to either let Jess come with him during the sessions, or he would report that I was being difficult, and stubborn, and unreasonable. I told him that I didn't care if he did. I told him that as long as he has a GF, she will not be welcomed at the therapy sessions.<br><br>Jess saw me arguing with Keith, and she walked over. She told me that she was very disappointed in me for keeping her away. She told me that she understands that I don't like her, but that she is his partner, and she has the right to know what's going on. She told me that she's been nothing but helpful and kind to me, and our son. She said that she has helped Keith be a better person, and father, and that I should be grateful for her. I told her that she's not welcomed because she's his new GF. I told her that she's a stranger to me and our son. I told her that I don't trust her or want her around. Jess told me that I was very mean and hurtful, and that she was just trying to help.<br><br>AITA here?