Baby bottle rot? How do you even bring it up to someone?

One of my close friends has a daughter who's almost 2 and she's been going to bed with milk in a bottle for a long time. When it started, I mentioned to my friend that putting kids to sleep with a bottle can lead to cavities. She said she wasn't worried because they brush her teeth really well.

I noticed over the past six months that her teeth have become more and more stained and recently, I think she has visible decay. I noticed her front teeth are really brown. The last few times I was over she gave her daughter Bear Paws right before bed and didn't brush her teeth.

At this point I think it's too late. I mentioned that I took my daughter to the dentist for the first time and she said she hasn't done it yet because "it's just baby teeth anyway".

I don't even know how to bring up cavities without overstepping or making her feel like I'm judging her, but this kid is going to have no teeth very quickly.