Aud, my answer is probably not what you believe you’re looking for, but it might be helpful to think outside the box. In your post, you refer more often to yourself than to you friend. That seems interesting. You say your friend needs to “broaden their horizons”, yet you are limiting yourself to only two choices, "help" (actually, you mean "not helping" if you don't lie) versus “lie” (is that really the best way to help?). There are almost always more than two choices in the real world, and that’s probably true in your situation.

Hi Aud! I think your question is not specific enough, the answer depends on many factors, for example: Does my friend really want to see the whole world? Mb travelling is not interesting for my friend at all? Mb he has other dreams and life goals? People shouldn't think that the lying is always the evil, sometimes lying can save someone's life.Also, lying and betrayal are different concepts, as I said before the reasons of lying could be noble, but there is no way to explain and forgive betrayal.