Friends without Children/Grandchildr en

Make time for your friend. If she is a true friend then she already understands the responsibilities you have to your family - she is just being honest in explaining how she hurts inside.
When you are able to spend time with her it is good to step outside the "family thing" and find other interests and pastimes to enjoy together.

I agree, try to avoid the subject. Talk about other people's grandchildren is boring enough for people who have got their own. For people who would have liked their own it is both boring and hurtful.

I wouldn’t talk about my children or grandchildren to someone who is childless. All the more so if they are unintentionally childless. Of course you don’t have as much free time as your friend, but obviously she carries a deep sadness at not having children and to talk about yours is insensitive. Try to avoid the subject unless she raises it. I’m afraid some grandparents talk of little other than their grandchildren - at best it’s boring, at worst hurtful,