It turns out she got to the venue early and had a medical emergency and rushed to the ER (her baby was fine, as we all know now). After the fact, she thought that her manager had contacted me and that everything was taken care of on the communication front.
So, as I suspected, it was a snafu...an emergency and a communication breakdown. Things were quite chaotic for them that night, I'm sure. I'm very glad to know that everything ended up ok.
I hope my experience didn't contribute negatively to anyone's perceptions of Holly. She's awesome. Her email was very apologetic and explanatory and I feel really bad that she got so sick before the show and I'm really glad she and her baby ended up ok. Things just got messed up with communications. It happens.