So sorry to hear this!
How upsetting! Just try and think that she had 3 wonderful years with you that she may not have had otherwise!
Yes, bloat usually happens in deep chested large dogs. A couple ways to try and avoid it is to feed 2 or 3 small meals a day, and not just one large one, and to limit exercise after eating.
Even with this, it may still happen. If a dog survives one episode of bloating, it will be prone to having it happen again. In this case, the vet usually tacks the stomach in place during the surgery to repair the bloat. This prevents it from ever happening again.
If anyone reading this suspects bloat, RUSH your dog to the vet.
Again, sorry for your loss!