Definitely not clear in English... Who would want to love someone UNTIL they are loved? I would assume this was meant to say: "I love her while she loves me"... Does this really make sense in Vietnamese? Thanks for putting the course together!
Edited: JCMcGee made a good point...
No, I don't believe this is that translation or the mike tyson quote.
This refer to some people that love someone when they feel he/she is not ahievable. When the person don't care, they feel he/she has more value, and want them even more badly.
But when the person pay attention to them, suddenly he/she looks more mundane, dependant, and them it's them who don't pay attention to their former crush.
I remember reading some quote (typically in a teenager notebook): "men are shadows: when you try to get close, the move far away, when you move from them they follow you" (and I felt sometimes the same, but about women).
There is also an Spanish theather play called "The Dog in the Manger", because that kind of person is like the dog that watches the food: it does not eat, but does not let other to eat either.
My contribution to the discussion: I checked the meaning with my Vietnamese wife. She confirmed the correct translation as given above. However, literally, it means that the "tôi" loves her, but stops loving her at the moment she starts to love him. This maybe is a too literal interpretation. I think in English you will never say it in this way (I am not an English native speaker, so I may be wrong). What the speaker really means to say is: I love her and I am patient and am prepared to wait a long time for her love to be returned (this according to my wife). I think you cannot give a literal translation when you want to reflect the true meaning.