Hello! Welcome to Share. I am sorry to read about the loss of your co-worker's daughter. I'd like to send you a virtual hug right now to let you know just how nice it is that you care enough to ask ideas about what to do. I echo ALL of what Lauren has written. Men do grieve so differently, but his angel is on his mind all the time. So true, that most think talking about their little one's death will upset them.
For me, it was more upsetting that people didn't ask. There is no good thing to say. Everyone has their own beliefs and opinions and this is one of those times to keep all of those to one's self. What helps? For me, that card 6, 9, 12 months later when everyone else had moved on and I was still so very stuck. Someone stopped and remembered that I was still trying to learn to live with this daily pain and navigate a future without my baby. If there hasn't been any mention of a memorial or remembrance, I might not go there. Not every mom readily knows how they plan to honor their child right away. You don't want to add stress. I'd go for more subtle gestures.
Humor, like a little note along with her favorite candy appearing on her desk when she steps away for a break. Could be something vulgar or naughty, something unexpected to break up the black cloud and depressive state. It doesn't have to be huge (!), just a little something to let her know that so many are thinking of her. On another day, someone could place a whole heap of that favorite treat on her desk with a note saying something about how the vending machine in the break room is on the fritz, etc. I'm trying to think of office-type interactions. If you go little items, keep 'em small. The last thing she's going to want is a bunch of f'n flowers and stuffed animals to carry to her car, you know what I mean?
Does she know about this site? If not, please share the website with her. I found it just several days after our loss and that was over 8 years ago. It was an immediate support system and really helped get some of those feelings out knowing that I wasn't alone in my grief. You're awesome for caring and even though you don't know her very well, she'll appreciate the thought.
Let us know how it goes:)