Hi EllenP,
I'm so sorry about your MIL. Please don't feel guilty. You do her a great service by writing here and reminding us that we always need to treat people well, but we know how difficult it is dealing with alcoholics. Often times the only choice is to pull away. I know, it's just so very sad. It's appropriate now to remember her good qualities, and not dwell on her problems. That's what you're doing, and that's the right thing to do, but that doesn't mean she didn't have some very serious issues, so please, please, please don't feel guilty.
Once again, you honor her with what you've written, and I, for one, appreciate that. I'm sure she would too.