It can take a long, long time for trust to build up again or to establish trust for the first time. Both of you made some poor choices, and her depression (and yours?) really complicates things. As a parent, I can COMPLETELY understand where she gets her mistrust from, and as a child myself I can also understand why you are disappointed and frustrated (my mom isn't the warmest creature on the planet). There is a probably a core part of your bonding relationship that is missing because of that depression and that makes me sad for you.
So, work on that GED and continue on the right path. I think that farm-hand prospect sounds wonderful. I hope it works out for you. Stay CLEAN. You have a second chance that many do not get; make the most of it. That GED will open doors for you and give you options. Not everyone has to take the perfect path to success so don't get down about it.