Why wld a girl u are seeing tell u she has some one yet wishes to move in with u?

for more explanation,she says her relationship with the guy she knew is not serious, yet treats u as her boy friend (controling n stuff) wants her opinion about things to be sort.And wishes to move in with u.Yet giving me the impression that all is fine with the guy she had known.Is it a kind of bluffing or she is faced with the problem of decision?The point is she at the same time insist on me having a long term relationship with her sister.Is this a kind of pretends or real love?Pls help me out.!!!1