Angel, I know just how you are feeling, earlier this month my cousin lost her 3month old boy also to SIDS they think. i felt there was nothing i could do to ease her pain. I have lost a Son too but i had a good warning, (we knew he had a defect..) long story short. all i could tell her at the funeral was that i was so sorry for her loss. I know from experience that i wanted the world to go on just like nothing had happened, i didn't want ppl to stop bringing their kids over or to stop talking about them just because i had lost my Son. when i talked to my Cousin she said she felt the same way. My son and her son were only 3 wks apart in age so i had to ask her if she was ok with meeting him 2 days after the funeral. anyway, just ask if there's anything you can do, offer to be of some help. and don't avoid talking about her Son, (you might want to ask if she's ok with talking about him first though). I hope that helps, i'm sorry to hear of her loss, i hope she can find the strength she needs to get thru these difficult times.
HUGS