People make me paranoid.

My boyfriend told me today about a girl who had messaged him on Instagram yesterday. He said when he opened it, it was a picture of just her boobs. And he replied back “????” She never answered him so he thinks she accidentally sent them to him. He showed me this from his phone so I have with my own eyes seen it. I told my older sister and she has now made me paranoid by saying girls don’t send stuff like that without being provoked. Now I’m actually like paranoid. Am I letting her get to me or is she right?