I hope she didn't intrude on your space while breast feeding. i was very uncomfortable with my MIL there. It was in the beginning and I really had no need for her to see me topless as I tried to master BFing. Not to mention she'd never done it so she didn't have any advice to offer. Just sat and starred at me while the lactation consultant helping me perfect the latch. When we got home I would retreat to the bedroom and lock the door and my baby ate every two hours.
No, she didn't come in, thank goodness. I think it actually made her too uncomfortable, which is fine with me. Just kept the door closed so that nobody would accidentally see anything on their way to the bathroom. She did want to come and "help" after delivery, but she puts partially dirty dishes back into the cabinets, doesn't wash her hands during meal prep, makes a LOT of noise, and is generally chaos personified. DH and I really didn't want anyone coming to help, even my mom, who is quiet, clean, and really good with babies. We wanted the first 4 weeks with just us to really bond with the baby and figure out our system and all. We didn't let anyone come for the delivery, either.
I'm so sorry that you had her staring at you -- that's totally weird, and would make me very uncomfortable, too!