This is more common than people realize or will admit.
As I get older I can recognize it better. It is a joke between my friends when we go out on how fast I can bust a girl who is trying to tell us she is single.
I have also been on the other side. When I was younger I was shocked that my gfs left me for someone else. As I got older I could see it happening, but the girls would not let me go. (the last one I was so happy when she finally found someone.lol)