Overreacting?

I need some advice. I am debating on leaving my 2 year old with her aunt who is 12. Grandma will be there as well as her on and off boyfriend and his daughter who is 13. But, the 13 year old has made mention that she doesn't like me, don't know why,don't care really. What bothers me is the 13 year old has said that one of my children should die (I have 3) because I have to many. Should I be concerned? Should I leave my 2 year old with her aunt when the 13 year old is there? or am I just overreacting? (When this 13 year old has misbehaved or said something distrubing she was just told to be quiet.)