Thank you all for your advice. I would really like to avoid getting rid of my dog if at all possible. I'm having a one-on-one trainer come to my house.
I don't think she's jealous, though she might be territorial. She never snaps at people outside of our house. Mostly when Peanut goes near her, she just walks away. Peanut likes to follow her though. Sometimes she growls and we correct her. The times that she has snapped at her have been once when Peanut cornered her, once when they were both on the bed and Peanut got too close to her (she was awake, just for some reason she didn't go away that time), and once when my husband had food he was giving to Peanut and the dog thought she should have it (she didn't actually get her that time). The times that she has bitten her, she hasn't actually broken skin. Though she has recently bitten me and broken my skin (I was trying to take off her sweater).
Ho-LEE crap. Red flag, huge big waving in your face. Doggy needs to go. TBH, one snap or growl here and the dog would have been PTS that day.
Mama, I say this all out of genuine concern. Why are you waiting until your baby is hurt? When will it be bad enough that you will step in an accept this is not okay?
This dog has issues. They may be correctable, but this is not something you have the luxury of working with. You have a child now. You dog is threatening to do real harm to your child. Respond accordingly.