Back to the OP: I think I'd welcome her over and squash her fears. Yeah, it seems a bit overboard but we don't have any idea why. I think it's odd that she didn't extend an explanation but she must have her reasons.
Now, as to the topic at hand: While I understand everyone's differing opinions on what is okay and not okay with sleepovers (or not allowing them at all), I think at some age, and 3rd grade or age 9 seems relatively appropriate, you need to assume you've taught your children some basic safety rules. While DD does not have her own cell phone and I don't insist that she call home before going to bed a sleepovers (this is a pet peeve with me but that's for another thread, lol), I do my best to trust her instincts and those things that I have taught her, one of those being that she can call home at ANY time and should never feel uncomfortable asking the parents/friend to use their phone, any time day or night.
I see that many of you would not let your children sleep at my house because you most likely will find me on the deck having a beer while the kids are watching Spongebob (Oh, sorry, wrong thread

) and we don't have a posted escape route. Of course, most of our rooms have windows, I know my safety route, DD and most other kids have been taught stop,drop,roll, and I only consume alcohol when I'm pretty sure I won't have to drive, the pretty much leaving a margin for emergencies that don't require an ambulance. Oh, and lest we forget, I have DS18 and a few of his friends hanging around trying to stay AWAY from the irritating, pre-adolescent 11 year old gigglers!
No offense please, just a stab at funnin
In all seriousness, I have an issue with single mothers who have men staying over that they haven't been with for a long period of time. I find this is not that uncommon. I am single but I would not have a boyfriend spend the night or left with your child (or mine for that matter) until I was VERY serious with him. It just gives me goosebumps to think what might happen and I know this is done quite commonly, a single mom trusting their kids to the guy they think is "all that" ~~ not in my house.