Hi and welcome!
I am very sorry for your and your sister's loss! You are welcome to post a tribute to Baba in our Rainbow Bridge section if your sister and you would like to.
When a piggy has died in the presence of their companions, then you need not show the body again; they will have taken their leave already. This only goes for guinea pigs that are euthanised at the vets or have been separated.
Toto is currently in deep mourning. Please weigh her daily and if necessary offer additional syringe feed. Since you do not know what Baba has died from, a vet check may be recommended to close out a health problem.
If she is not eating and drinking at all and is not ill, then she is what we call 'pining acutely', which is is the extreme and potentially deadly form of mourning, as piggies can give up on life. Most well bonded piggies are withdrawn in the first days after a loss but they will still eat enough to keep themselves alive. Acutely pining piggies urgently need company of their own kind to revive their spirits and zest for life; with other bereaved piggies you have ideally 1-4 weeks to find a new friend. If you can adopt a piggy from a rescue, ideally by allowing Toto choose who she wants to be with before bringing home a new companion, that would be great. Companionship is absolutely vital for guinea pigs; they are after all group animals and not wired to live alone.
You and your parents will find the tips and resources in these two links here helpful:
Looking After A Bereaved Guinea Pig
Human Bereavement - Grieving, coping tips and support links for guinea pig owners and their children
PS: While carrots are safe to eat, they are actually not good in large quantities on a daily basis. It is like having your piggies on a diet of fatty life shortening burgers. It is not likely that Baba has died directly from this (a heart attack, a stroke or acute heart failure are more likely), but please have a read to make sure that Toto stays as healthy as possible.
Over 80% of the daily food intake should be hay, more hay and as much as hay as you can get them to eat - that makes sure that the crucial back teeth and the guts are working optimally as that is what guinea pigs have evolved on; a hay based diet really makes a huge difference on general health and longevity. Only 10% of what your piggies eat in a day should be a balanced mix of veg that provides a wide range of additional nutrients, especially vitamin C, magnesium and trace elements. Pellets (and not a dry mix) should be only a teaspoon per piggy per day.
You can find a pictured sample diet and a list of what piggies can eat how much and how often in this comprehensive diet guide here:
Long Term Balanced General And Special Needs Guinea Pig Diets
We have lots more interesting and very helpful information on a wide range of topics via this link here, including a guide to piggy whispering so you can console Toto in her own language.
Getting Started - New Owners' Most Helpful Guides