It's important to be vulnerable. The willingness to be vulnerable leads to close relationships. One can't always be in defense mode.

In this instance, if you saw why she might have acted in that manner, while you would likely have been very disappointed, it might not have raised to the level of you being hurt. These are all aspects of emotional intelligence. Now that you may see what happened in a different light, you may have gained emotional intelligence to handle some future situations differently.