I have the same problem as u, but there is also another thread
about it, though there is not much info as to why she thinks she is
possessive.
Anyway I told off my gf, and said dont talk to me for 3 days, today
is the 3rd day liao, so far so good. Sometimes i feel u need to
assert your right for some personal space. if not, she will think
that whatever u say can be ignored, and wont take u seriously in
the future. U need to show her u really mean what u say!
Good luck!