L.C.
I am so sorry for your hurt. It's hard to lose a parent even in the best of circumstances. I'm going to tell you what I believe. I believe that your mother knows that you loved her the best way that you could. When you live in a dysfunctional world it is really hard to express functional love. But just like you know it wasn't perfect and wasn't what you wanted at the time, NOW you can see past it, SO CAN SHE.
You can't go back in the past and change what was. What you can do, now, is write down everything you needed to say, good or bad, and read it out loud like you are saying it to her. You can say, "Growing up was hard because....(insert your story here), but I want you to know that it's okay and I'm okay, because 364 days out of the year I am happy. I have a great marriage, beautiful children and a full life. So if you had never done anything but bring me into the world and make sure I lived long enough to find this man and have this life then that's enough and I thank you." Then make your peace and let go of those things you cannot change.
Add to it, by honoring her in a way that makes you feel good every year. If she had a favorite flower, adopt a senior citizen at a retirement home every year and present it to her. If she liked animals, donate a day that week to volunteering at an animal shelter. Do for someone else what, for their own and equally valid reasons, her children aren't doing for her.
You had a really hard time and did what you had to do to be OK. There is absolutely nothing wrong with that. If it hurts you right now, then use that energy to do something positive in a world that could certainly use a lot more positivity. You will feel better, you will set a great example for your kids, and you will honor her long after she was here to honor.
With hugs and prayers,
L.