infant tooth decay from prolonged nursing

My daughter is 15 months and just today I noticed a lot of plaque on her top four teeth and what appears to be decay. She still nurses, and cosleeps which means lots of suckling still at night. She is a really good eater and I'd be lying if I said my kids never ate Popsicles or ice cream or anything with sugar, but not often. No soda and no juice. I'm really feeling like shit about her poor little teeth. We're going to the dentist in two days but I'm so worried. Anyone experience this? Thanks in advance