JBird - it's perfectly acceptable and understandable to have feelings of frustration and resentment. We're human beings, and our feelings aren't always pretty. What we do with or about those feelings and the actions we take are what's important here.
I did a Google search for "Buddhism resentment" and there were oodles of hits, with quotes from Buddha regarding resentment and mindfulness exercises to reduce/work through feelings of resentment and anger. I think my favorite of the quotes that I came across is “Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else—you are the one who gets burned.” It's very similar to the quote "Anger is like drinking poison, expecting the other person to die."