I'm gonna be disagreeable.
Does her mom know your group well? If not, then try to get to know her better and try to get on her good side. Also, contrary to popular belief, con-land isn't the bright happy land everyone thinks it is- a lot of bad things could and do happen.
And to answer your question, yes, I have been ditched at a con before. It's really upsetting and I was seething about it for hours.