You may be natually worried about her and these dreams pop up. The way the world is today it doesn't hurt to watch her carefully anyway. As much as I hate to admit it there are sick people out there wanting to hurt our kids. Just watch your sister make sure she's safe and hopefully the dreams will go away. You're terrific for wanting to protect your sister
Unless you genuinely believe that you are predicting the future, then I don't believe you need to be worried. However, I don't think it would hurt to keep a closer eye on your little sister till your worry passes. Better safe than sorry.
You should not be worried you probaly had that same dream because you were worried about her and couldent get her off your mind but if you are that worried check on her once and a while to make sure she is ok
to me that means you are feeling guilty about something be it not spending time with her you know sisters need to ask alot of questions an maybe you need to tell her you love her an your their for her if she needs you no matter what !!