Gosh I know how you feel. My 17 month old gerbil passed away on the 19th. He was just lying at the bottom of his cage and he was rather thinner than he used to be in his prime. I tried to bottle feed him some food but sadly he was already getting cold. I did everything to keep him warm but sadly it was just his time. I tried to revive him but to no avail. I buried him in the garden the next day.
He left behind his brother, who I introduced to his own son and they both got on instantly. The gerbil who passed away also had 3 sons, one who looks like him, so he has left behind a great legacy.
You will always remember them, but the pain will get easier to deal with over time. She is in a better place now, or at least it helps me to believe that when it happens to my animals. Do not worry, you did your best.