“She’s in the best place now.”
No. No matter how bad things were, how horrible the disease, the best place for a child is in her parents’ arms.
“It was meant to be.”
No. Sometimes the most terrible horrible things happen for no reason. Trying to find some sort of divine meaning in the death of a child is just adding torture to the pain the parent is feeling.
“You’re young, you can have more babies.”
Next time you are at a funeral where a woman is burying her husband, tell her that she’s young, she can go dating again, there are plenty more potential husbands out there. No? You don’t think that would be a good idea? So why would you think it’s acceptable to tell a parent they can replace a dead child?
“At least / be thankful”
No. There is no way to reduce the grief of losing a child, and trying to downplay is just makes you look like a dick.
“Time heals all wounds.”
It doesn’t. If you lost a leg, time does not make it grow back. Losing a child hurts worse than losing a leg. The pain never goes away. The best you can hope is that you learn to live with it.
“I know how you feel.”
Unless you are a bereaved parent, then you don’t know. Losing a parent or a pet is not the same. No matter how much we love them, we know that we will outlive them. No parent expects to outlive their child.
What you can say
Nothing. Give them a hug and be there for them.
“Tell me about her.”
You are not going to upset any parent by talking about their dead child. You’re not going to remind them, they will never forget. They do want to celebrate what they had of her life.
“I remember the time…”
Share your memories. It helps.
“I brought pizza / I’ve hung out the laundry.”
Life goes on, and food and laundry are necessary. Don’t say, “I’m here if you need anything.” Instead, offer to do something specific.