That may be a good idea, or maybe this might be the case. Maybe they've gone out once or twice and he feels that they're dating exclusively while she feels it's something far less serious. She may just not think they have what he believes they do. Of course this may not be the case but with her still flirting with you heavily it makes me wonder. Either way if you decide to pursue anything you're going to have a heavy risk of pissing off your friend that you're moving in with.

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Heit ist mein taug.