That is a game to be worried about. Lots of developers have tackled this problem and come up short, either making her a Goddess that doesn't warrant your care like Elika. HL2 of course had Alyx, and did some really beautiful stuff with creating and dissipating that sense of loneliness, but within the actual game, she's not very meaningful at all, she'll occasionally surprise you by reacting to something like you shooting a TV, but then she'll completely ignore you shooting around her or throwing shit at her. Yorda was amazing, but had to be so abstracted from the real world that her actions within the game wouldn't seem completely absurd.
No one has done it right in the context of a real relationship. Considering everyone is going after it, it's going to be done sooner or later, maybe this, maybe LToU, maybe HL3, I can't wait to see who it is.