So she isn’t really Buffy sister
She just made up to life to be in the family
They all seem to remember her so where was she to them all this time for years with the father
It seems like you just began season 5 and, as you should, got confused with the episode "Real Me." Just keep watching and it will be all explained.
Rhey created her to life, giving anyone who close to Buffy memories of Dawn. Even same blood of summers, so she was with her father during the divorce in Buffy and mom and everyone minds
Just asking a yes or no
Finish watching the season. It very clearly explains in clear detail where she came from.
What do you think?