If that were me, I would not send my girl to sleep-overs yet. My girl is 5 too, and I think it's too young. The only place I would let my girl go to, at this age, is her Aunty's house or my best friend's house. That's all.
It's not just a matter of age or personality. I think the age difference is a factor, and you yourself has never been to this woman's house....you don't really know how it would be for your girl, and you don't really know this woman well...you didn't say she was your "friend." Frankly, nowadays... I think pre-school age is too young for sleep-overs at "strangers" homes....what would the sleep arrangements be? What are the activities? What is the supervision there? What are the rules?
My friends daughter once went to a sleepover, at a friend's house. It turned out all the kids slept in one big room, and there were other adults there, whom she did not know would be there...the adults were drinking etc. One man got a little too close to one of the girls and tried touching her. Yes, a terrible situation... and the other parents were NOT aware of the activities in this house, much less the "parental" quality of care.
So... think about it wisely. Go with your gut feeling, not "peer" pressure.
Good luck and take care,
~Susan
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