1) She treats them as if they are her parents.
2) She treats them as if they were her parents.
3) She treats them as if they had been her parents.
a) She treated them as if they were her parents.
b) She treated them as if they had been her parents.
Well, I think only in 1 and 2 we are sure that they are her parents, but I wonder whether a can have the combined meaning of 1 and 2, that is, "they are her parents, or they are not her parents, or we do not know whether they are her parents or not.)
In the others either we do not know whether they are her parents or not or we think they are not her parents, but we do not think they are her parents. Then, what is the difference between 2 and 3 and a and b? Thanks.