You will not like what I have to say, but since you asked for help, here it is.
Poor me! Everything about your post screams 'poor me'. sheesh - what a victim. Get over it. Stuff like this happens to everyone.
There are all kinds of people in the world and you have to learn to deal with them.
Right, now onto the resentment part and how to let go.
Check out something called EFT (Emotional Freedom Technique) It will help you get rid of that resentment and quickly too. The website is www.emofree.com and there is a free manual which explains everything. It literally takes 15 minutes to learn and 2 or 3 minutes to do. Simple and easy. There are videos to show you what to do too. When you are able to look at these things calmly and clearly, you will see that it is just not worth spend the effort to get worked up about it.
There are EFT practitioners who often give free initial (short) sessions if you want to try it out. It is a very powerful technique and should be able to help overcome the resentment and holding on to grudges.