Hi lozza............"Does not seeing her make me a bad and horrible person?" that would depend on why you didn't go. But it's not that you don't care is it, in fact it's the very opposite of that by the sounds of it. It's because you care so much, so how can that make you a bad and horrible person??!!
But you know that not going isn't going to make anything any different, right? So perhaps try to have a think about what might help you through this time, and what might make you feel better when you look back on this time in the future. Of course that can be really hard if not impossible to tell but at least if you've considered it now.
It might be you want to ask a family member or friend to go along with you (and either stay or not stay with you), it might be you want to just stop by very briefly for a last "goodbye", it might be you ask someone to take in a card with a personal note in it for her, it might be if you're religious you just want to pray for her, it might be that you want to just try to remember her the way she was/have those to keep as your memories of her/keep those to honour her (and there's absolutely nothing wrong at all with that), or it might just be that you can't visit because it's too painful and no-one (least of all you) should judge you on that. The main, most important thing is how you feel about her........and that says everything about you, her, her life as you knew her.
And as for your drinking when your Grandpa died, well your Grandma would have probably understood your pain, right? So if you're thinking you could have done more.......well she probably would have understood some of the reason why.
And the drinking..........do you think you need some support from maybe the AA right now, not just because of the drinking (if you are now or not) but through this difficult time in your life with/without the drinking??
Anyway, let us know how it's going for you if you're able to.
Here for you

Alison