Our puppy died- UPDATED WITH PIC of PEBBLES

We bought another puppy like 3 weeks ago and yesterday she was acting really weird so we brought her to the vet. They said her sugar was really low and she would have to stay overnight. She seemed to be doing well but the vet just called and said she took a turn for the worse and she passed away. He said she had a parasite also. I am sitting in my office crying and I dont know what to do.