my mother is stressing me out-

My son was born on the 26th but has been in the NICU since then due to an infection from my water being broken for a prolonged period. I've been pumping milk for him, and supplementing with donor breast milk and attempting breast feeding when I can. He is due to come home tomorrow and my mom is stressing me out to no end. She keeps bringing up formula, asking what I'm gonna do if I don't make enough milk. She thinks because I can only pump so much that he's only getting that much, and I can't get her to understand that babies can pull milk from the breast better than the pump. She acts like he is going to starve the second we leave the hospital. I'm trying not to stress because I know it can affect my supply but I'm so frustrated 😑 I've told her everything I know repeatedly, I've sent her countless articles, even had her in the same room as me and the lactation consultant and the occupational therapist and she still acts this way. When she had me, she didn't even try to breast feed and so she isn't very educated when it comes to it. I know she's concerned but it stresses me out. She's definitely the kind of person to sneak behind my back and feed him formula if she thinks he's still hungry. Any advice on what I can do to ease her mind?