Sounds more to me like she has entered the bratty teenage years. She is still a baby. She will grow out of it. Maybe she senses something untrustworthy about your friend. Cats are said to be very intuitive. As are dogs. I would not think it's about her being spayed. Some of mine have their cranky moments too. In fact most do. I just ignore them for a while. They soon come around again.
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!