I hope she's already back... but cats can go awol and return after quite a long time (one of mine once disappeaared for almost a year, but that's another story.) They can be very clever at finding food and water as long as the weather is reasonable.

Have you called the local shelters and vet offices? Keep calling everyday to check for new arrivals. You don't want to miss her because a message did not get passed.

Putting food and water outside your home may lure her back.

It is possible if she did not see her animal friend's death that she has gone looking for her friend. If you have a blanket or crate the other pet used putting that out where she could smell it might help lure her home.

I seem to remember you had her spayed, otherwise I'd say she was off to make more babies. If her kitten is 3 monthes, she has not really forgotten her, but the tight bond to an infant is over. At that age, mom cats feel that the baby is up to hunting trips and life on their own in a safe envirnoment which you have given her. She trusts you to mind the baby and the baby to have basic skills. When she comes home, she will resume her relationships, but in her world her baby is an early teenager, not a toddler and will be treated that way.

If she lived an earlier part of her life as a free-stray or a feral she may have gone on a walk-about now that baby is old enough and will come home when she has satisfied her urge to hunt and wander.

I know you are doing all you can think of, it is so frightening when they go missing (which is why all mine live indoor lives these days). If you can walk the area at dawn and dusk when scents are best and it is quiet calling for her and listeniing for her reply you may get some results. Check culverts and bushes near the road. Hopefully she is fine and safe, but if she has been hurt she may be hiding and quiet to try to stay safe. (I've found cats this way it does not always mean disaster.)

Good luck and many prayers. Cats are good at find home.