Do you think it's possible that she didn't see the message, or saw it and there was some technical glitch in replying or something? That has happened a few times with my therapist. If I don't hear back from him within a reasonable amount of time I usually contact him again and then he usually tells me that his phone was problematic or the return message hadn't sent properly or something. It's always worked out to be a technical problem or an oversight.

But I know how painful it can be not to hear back- I really hope you will go to the session and find out why she didn't reply.