It's hard to say without knowing the possible ramifications of this person being there. Sounds like she once worked there and now doesen't, and there was an issue in her leaving, or something of the sort, prompting her to phone you with a heads up she was coming back? Of course I understand if you dont want to air all the details of someones situation online.
I think I would just go with my general rule, for when those not family or not close friends lie or otherwise betray. I keep it polite, but just don't trust them as much or seek closer friendship with them.
Your story reminds me of when I was working at a particular place... Everyone in the store knew the manager had parties and this co-worker and that co-worker over in the evenings to down as much brew as they could manage. I was invited and went a time or two, stupid as it was.
All anyone could ever talk about the next day in the store was how funny they got the prevous night.
So this one day, I started work early in the morning.. and late in the afternoon, the other shift leader was supposed to come in. He didn't come in, and I called and called, as I was stuck working in his stead. He finally picked up to tell me, in a laughing tone.. that he was really sick and couldn't leave the toilet. I called the manager as well, left messages... and he called me back an hour later to tell me the guy was having family issues... while I heard music in the background and the co-worker yelling "Tell her I was in a motorcycle accident" ... laughter.
So I called the owner of the store.. and who had to come in to take over for me, but the lying manager... swearing up and down that he was just telling me what the co-worker dude had called to tell him. Yeah.
So the next day at work.. everyone is in an uproar over all the hilarious things the co-worker and manager had said and done
. Yeah.
I still worked there.. and was polite every day after... but I made it clear to the manager that next day back, if that ever happened again, I was walking out the door when my shift ended and locking up behind me.