well, i will be honest!
first of all sympathies and prayers to this family. :(
i think that this is fine. you say that this friend with a baby called this friend who lost her baby to make sure it was ok. you dont say what your friend may have decided or told the new parents, but it doesnt matter; if your friend who has lost her baby is ok with it, then theres nothing more to say on the matter. you arent her, you dont know or understand how she feels, and you dont have a right to tell anybody your opinion on the subject.
this new baby is 5 weeks old. i hardly leave my THREE YEAR OLD someplace, i would NEVER have left an infant of that age with anyone! her parenting instincts are telling her not to separate from her baby, and that is good. she shouldnt have to be forced to if she doesnt feel its right. newborns of that age mostly sleep or eat anyway, so whats the harm? and what a better way to honor your friend's lost child than to have your own to hold and become even more grateful for?
basically, you are out of line to be thinking of this kind of drama at a time like this. if you feel you would be willing to leave a 5 week old baby with someone else, then thats your opinion and you have a right to do that. this mom however does not feel this way, and she did the respectful thing by calling your friend and making sure it was ok. someone else having a baby doesnt cause pain, losing your own does. that pain never goes away, its going to matter very little if she runs into your friend now with a baby at 5 weeks than it will if she runs into your friend later with a baby at 2 years old. shes going to think of her baby every time, probably more so than other babies, because they are so close in age.
either way, it doesnt matter all the details. if your friend said it was ok, then its ok. shes not you. if the time ever came for you to go through this (God willing it wont EVER) then you would have the right to say no. but right now, this time, its really not your issue.
please concentrate on being there for your friend. i know you are, but dont let this kind of petty thing get in the way of being able to mourn yourself! yes, even friends have to mourn this loss! forget about this for a minute, hold your children a little bit closer, and be there for your friend; and i dont mean just talking . make some dinners, help them clean the house or do other chores, go to the grocery store for her, help her out in other ways. just concentrate on YOUR friendship with her, and the things that you can do, not what someone else is doing.
:) :) im not mad. i just thought i would be honest. its ok to feel the way you do. it does seem like its wrong to bring a baby to a funeral for a baby. but if your friends have spoken about it, then thats all that needs to be said.