Pregnancy: Second Trimester Community

Yesterday at the doctor's office, my mom and sister decided to pop up and surprise me. I hardly see them and they know that I go to the office every other Friday. It was a little weird because DF wanted it to be just me and him. At the moment, I was in a room doing a volunteer study. DF refused to go to the waiting room to show them where we were. The nursing staff eventually led them to our room. I'm pretty sure there were some privacy violations there, but I digress. After the study was done, I had to go back to the waiting room because I still had to have my ultrasound and OB appointment. The waiting room was full and I wanted to sit by my DF and mom wanted me to sit by her. She said that DF can just stand up. I was shocked at that. She was being so mean. To make a long story longer, I told her that she cannot come into the room when I have my ultrasound, but can come when I see the OB. I really wanted some special alone time with DF at our peek of the LO and we are both on the Yellow Team. My mom really wants to know the sex though. I was scared that the tech would hint or tell her, and my mom would eventually leak the info. Even though I told her this before I was called, she still tried to come back. I had to push her away from the door, like three times!!!!

I said all of this because now I'm wondering if she knows that she will not be allowed in the delivery room. I only want my DF there with me. Did any of you tell your parents ahead of time of your plans in the delivery room or just wait until that moment and let the staff handle them? I don't know how to tell her that she will not be allowed in until the baby is born. Any suggestions?