Is it even wise to try to build up trust again when the person already has betrayed that trust?
This will depend on whether or not the other who has hurt you shows what I call in my book, The Forgiving Life, the “three R’s.” Does this person show remorse (or inner sorrow), repentance (coming to you with a sincere apology), and recompense (trying to make it right, within reason)? If the three R’s are in place, then you can begin to try to re-establish trust, which can be earned one small step at a time. See if the person can handle the particular kind of responsibility that did not materialize in the past. If, in the small steps, the person shows a good will and sound behavior, then you might trust in more substantial ways. If the person cannot handle finances, but you give the person now a small responsibility with finances and this is handled well, you might consider a little more financial responsibility, and then a little more. Trust needs to be earned and is often built up slowly.
For additional information, see The Forgiving Life.