I would never call you "stupid", as you said some have about this line of reasoning, but I would call it misplaced. IT is natural to want to blame someone, and since God can seem distant at times, He is an easy target, albeit misplaced. Now, let's handle the factual part of this. God did not invent cars, nor did he "cause" the wreck to occur, so God is not to blame; this is 100% driver error, either on the part of your grandmother or the other car she hit, or perhaps there were bad road conditions, but no matter what the case, it is stil not God's doing, thus God cannot be blamed.
Secondly, you said she did good deeds, and works, and all that, which is nice, but it has nothing to do with salvation. Salvation is a personal decision that someone makes to accept Jesus into their heart, which works has no impact on at all. Also, that is something you can never know or judge and is 100% up to God. All you can do at this point is dive into the Bible...which is what I recommend to people going through hard times. Try reading the book of Job, and you will probably feel better about your situation...he lost everything, including his family, fortune, and health, yet remained faithful.