Oh my.........I am so sorry.
Your story was so sad to read, but it is all a very possible part of breeding. I agree with all that Yorkiemom1 has told you. There are any number of reasons for the pups death; a mom and pups need to be monitored closely for the first week(s) for any signs of distress.
That being said, the question to breed again should be determined on whether you want to try again and/or whether you want to put Bonnie through another pregnancy. Once Bonnie recovers from this pregnancy and the loss of her pups, she will not remember any of it. She will not long to have other pups, it doesn't work that way. As far as how long to wait, obviously you will have to wait for her next heat cycle, which in some cases is okay to breed again right away, but many will skip one before breeding again. I feel age 5 is a good age to retire them from breeding, so maybe spaying her after this would be a good choice. If you and other family members are looking to add another Yorkie to the family, maybe find one through another breeder & let them do the work for you.....