PF- My mom wanted to be there so badly. I know it would have meant the world to her, and I know that it really hurt her that I didn't want her there. BUT, giving birth was SO INTENSE, and I knew that I couldn't handle having anyone or anything there that pushed my buttons. My mom sounds a lot like yours. She's very loving and she means well. But, she's incredibly overbearing, very negative, and has ABSOLUTELY NO BOUNDARIES. None.
I was at home for almost all of my labor, with my DP, my good friend (who was acting as our unofficial doula), and one other friend, who basically stayed out of the way and ran errands for us (walking the dog, bringing food and water). When we finally left to go to the hospital, I had my friends call my mom to tell her that I was in labor, and to meet us there. When we arrived, I told my midwife and the nurses that she was not allowed in the birthing room. I know that this sounds harsh, but seriously, I just could not handle interacting with anyone else, and...I don't know...I just wanted the birth to be wholly "mine." My mother constantly co-opts my stories, experiences, etc., and tells them to the world. I just wanted the birth to be MY story. As soon as DD was born and we left the birthing room, she was there to meet us. And when we arrived at the hospital, my doula friend came into the birthing room with us, and my other friend hung out in the waiting room with my mom, so she wasn't alone.
Anyway, that's my $.02 on it. It's YOUR birth, and it's one time in your life when it's completely okay to just ask for EXACTLY what you want, and not feel guilty about it at all. (My mom is the queen of the guilt trip, so I had to really work on this...)
And, jjnoho, I would really recommend a doula. My DP was skeptical that we needed someone else, but it turned out to be a lifesaver. If you're in labor for 8 or 10 hours, your DP is going to need to pee, eat, drink, stretch, occasionally. It's nice for both of you to have someone else there, making sure things are okay. Your midwife probably won't be there the whole time- they tend to show up for active labor and delivery, but not for all the handholding beforehand.