She did the same to me once too. Albeit with longer notice, bumping me for another guy even though I'd seen her a few times prior to this so she knew me and I was a semi-regular of sorts.
I booked her the day before for 1pm the next day, she goes definitely.
I confirm the next day at 11am for 1pm, and she texts me:
"Oh sorry Hun, I wasn't sure that u will come and someone already confirm the booking yesterday but I can see u at 2:30pm."
Shows she has consistent behaviour for this then.