MIL invited herself to my ultrasound - am I over-reacting or is she overstepping?

Let me start off saying I love my inlaws very much. They've always treated me like family, even when hubby & I were just dating. We're preggers with our 2nd baby & we have an ultrasound to find out the . Hubby works in the family business & I want him to be there with me, so I brought up the utrasound appt to see if he could get off. MIL quips up & invites herself to go with us. I was too shocked to say anything. Hubby is happy as a clam and says "Sure!". I wanted this moment to be just me, him & our daughter. We are bringing a tape to record & share with the rest of the family. So why can't MIL find out with everyone else & let us have our moment? I feel like she has over-stepped several boundaries over the course of our relationship...she disinvited MY family from my dd's 1st birthday. She made a Dr appt for my hubby when I clearly told her I had things handled & I would make the appt after talking with him. She came to the appt with us. I felt like she was undermining me.