Oh my gosh, I was in the same boat as you last year (I still am now). My sister and I didn't communicate well during the first half of her pregnancy. Where I thought I was helping, she thought I was invading. It was difficult to find that line. We talked and she told me 'just ask me first, don't just do it, ask me first.' and that's how we figured things out. I would go to her and say 'is it okay if I do this?'
the MOST IMPORTANT QUESTION I had to ask was whether I could touch her stomach or not. She was NOT a fan of anybody, even her sisters, touching her stomach without asking.
Really what you have to do is just ask 'is it okay if I ________' She will let you know.