To give advice or not to give advice?

My brother in law, his girlfriend, and their 6 mo baby just moved in. We are both new moms but I am ten years older and her mom was raising her baby until recently (we moved them in so they can learn independence and adult responsibilities), so I’m doing my best to lead by example. I don’t want to step into situations that aren’t my business nor do I want to come off like a know-it-all because like I said, I’m a new mom and I know it’s a learn as you go experience. I would never tell someone how to parent. But some of the things she does really make me cringe and I’m not sure if I have any place to step in just to offer friendly advice. She doesn’t wash bottles, just rinses them and calls it a day. The baby sleeps with pillows and blankets.

This is the one post where I’m really asking what I should do or if I just do nothing. I just want to help without being out of line.