Mixed signals?

I am meeting up with an ex girlfriend of mine, and i am geting some mixed signals form her. When I texed her to see if she wants to go and have drinks with me she seemed real exited, but when I phoned her later in the week she sounded like the grim reaper. How do I know if she realy wants to go out with me? I am not interested in hooking up with her again, so should I cancel? I need some female advice pls.