She used my sonogram pictures and said it was her baby

I announced publicly that I was pregnant and my sister's ex friend screenshots my sonogram pictures and posted them on social media. She is supposed to be pregnant with her second child but my sister always suspected she was lying about ever having a baby or being pregnant. When she "gave birth" to the first child my sister asked to come visit for weeks after the baby was born and she had so many excuses as to why my sister couldn't come over or see the baby. She is pregnant again and is acting weird. I literally posted to Facebook and less than a hour later I see my pictures all over her social media. When I asked her to remove the pictures she act like it was an insult and told me that they were her pictures. My name are on all of my sonograms so if you zoomed in my name are on them. She deleted them and then acted like she never posted them. My sister started to snoop and ask her friend's sister about her first child and the sister came right out and told her that her sister never had a baby. This is so weird and very inappropriate. Because she is posting pictures of a little girl on social media saying it's her child and calling her the love of your life. Her sister stated she didn't know about that so my sister sent her of the little girl and come to find out the child belongs to someone else. I don't know what to say or do. This is insane😒😞😞 ( excuse my improper spelling I was so annoyed that I was typing really fast and not thinking about what I was writing to her)