Trust is a hard thing to lose. When you think that someone is in your corner and you find out you are standing alone, it is a painful thing. A situation like this does do one thing and do it well. It absolutely teaches you that as long as the no-longer-trusted is in the vicinity, you will never, ever confide in - or ask for help from - the one who betrayed you.
This is a hard lesson to learn when you are learning it for the first time in a young life. (And I can speak from personal experience that it is still hard to live through no matter how old you get.) But the absolute most difficult part of the equation is that you must immediately decide that you will not allow one betrayal (or two, or three, or fifty-three) to affect your ability to open your heart to the next person. Keeping your heart open is what makes us distinctly human - and vulnerable - and capable of deep and abiding love. And that kind of love is only possible when you take the risk of opening your heart - no matter how many betrayals have taken place.