Hi Bronte's Mom,
Welcome! I am SO, SO sorry about your precious Bronte's sudden death. I feel SO connected to you!!! I came to this forum on October 3rd with almost the same story as you. In fact, my post was titled "Does It Ever Get Better?"
I had a "daughter" and "best friend" that was close to turning 12 years old, that I had to "put to rest" suddenly. Rachael (a black labrador) seemed very healthy to us. She had started developing arthritis and did move slower when she got up and down. Her appetite had slowed down, but we had just started her on arthritis medication and blamed that for her decrease in appetite.
Then, one Tuesday night, when we got home from work, she wouldn't eat at all. She didn't eat her breakfast and wouldn't eat her dinner. She seemed to be moving even slower than "usual". We took her to the vet. We were horrified to discover after blood tests, that her cell count was extremely low and indicated internal bleeding. We tried medications, hoping it was an ulcer, but feared it was cancer. By Thursday, when she only got worse, we knew our worst fear had come true, and it was from cancer. By Saturday morning she couldn't stand up, wouldn't eat or drink and her breathing was louder, like she was struggling. I had to take her the vet that morning, on October 2nd. We only had 4 days to realize she was very sick, watch her go downhill SUPER fast, and let her go.
Just like you, I struggled with extreme guilt! I kept blaming myself for not discovering earlier how sick she was. I kept telling myself that I could have saved her life if I had known earlier. She was SO strong for us, that she never showed how sick she really was, until she became so weak she couldn't hide it.
What you are feeling is normal, though. I totally understand the shock and disbelief you are feeling now. Please forgive yourself, though! You didn't do anything wrong. Your precious Bronte was like my Rachael, they stayed strong and devoted for us, right up until the end. You certainly couldn't have known just how sick she had gotten, until she could no longer hide it. As soon as you realized she was sick, you took her right to the vet. Just like us, you did the VERY best for her that you could. There is NO way to ever get any answers to the questions we have about saving them if only..... So, for your peace of mind, you have to accept that Bronte got sick and you and the vet did the very best you could.
Your Bronte is no longer suffering now. She knows how much you love her and that you took the very best care of her. You gave her a WONDERFUL 12 years! Take comfort that she never had to know the pain of starving or sleeping in the streets because of your love.
Finally, to answer your question about getting better, yes it will.

I know everyone in here told me it would get better too and I just didn't know it ever could. But it's been 4 weeks and 5 days, and I can get through the days without crying as much. Oh, I still hurt and I still cry, but the healing is starting now.
I know these wonderful and special friends in here will give you much better advice than I can, but I just wanted to let you know that there is someone else here that felt the same way you do now, and I AM getting better, just like you will. Time frames vary for each person, but I promise you it will get better with time. I believe that the sooner we forgive ourselves and stop asking the "What if..." questions, the real healing will start. The pain and loss is already SO hard to deal with. We don't need to beat ourselves up with guilt on top of all that too.
Big hugs for you!
Cheri