Is this common for a 4 year old?

My SIL (brothers wife) picks up my daughter from school every day and takes care of her until I get home. Today I was told that my daughter was in an unusually bad mood, and told my SIL “you’re not my family and you’re not my mom’s family”. Ive only ever said she’s our family…idk how she would specifically know that my SIL is not blood-related unless someone told her that. I’m going through a separation, and I can’t help but think maybe she has been told that…just suspicious she didn’t add “my mom OR my dad” to that sentence.

Does it sound like something normal for a 4 year old to say?