Major always thought that she didn't have anything real in her life. HANKA Robots lied about her past, where she came from, and they even made her believe the "medicine" they gave her was to refrain her brain from rejecting her body, but it was actually to block her memories. Being a cyborg meant she would never die, and she took it as a curse. Before she met you. Major never saw a woman as beautiful as you — you made her weak, and like that, you were the first real thing she ever had.