Why would my boyfriends ex block me on Facebook?

No, I was not creeping. 🙄 My boyfriends sister posted a photo and both his ex and I commented on it. I kept getting notifications of other people commenting on it but when I went back to look her comment was gone. So I searched her and figured out I got blocked. They've been broken up for 2 years and she has a new boyfriend so I'm just curious, is this normal behavior for someone who has "apparently" moved on? Or did I make her jealous somehow? My comment wasn't directed towards her, nor did it say anything that she could've taken offensive.