I would much rather think of it the other way around. As far as I know the average person is exactly as nice as the average person is. However, when she said she believed people are nicer than they actually are i guess it is because her estimation of the average niceness of a person is biased and she is actually falsely believing people are worse than they are. This might well be some kind of defense mechanism she developed. Of course if you expect worse than average, the chances of you being positively surprised are way higher than the other way around.
I would much rather think of it the other way around. As far as I know the average person is exactly as nice as the average person is. However, when she said she believed people are nicer than they actually are i guess it is because her estimation of the average niceness of a person is biased and she is actually falsely believing people are worse than they are. This might well be some kind of defense mechanism she developed. Of course if you expect worse than average, the chances of you being positively surprised are way higher than the other way around.