I agree this lady doesn't come across well but, there is truth in that childless and single people are often treated as less than by some parents and couples. I want to caveat this with the understanding that of course parents and couples will prioritise their partner and kids. For single, childless people friends are really really important. If we don't see our friends we are alone. For people in relationships or with kids (of any age) often they will usually always have company so don't feel the need to socialise much outside the family.
I have felt an underlying vibe from some friends with kids that I'm somehow not a serious person with an inner life, that I've not grown up in some way.
I get that parents are often knackered and don't have the capacity or want to meet up much but to be on the receiving end of that kind of friendship can feel very diminishing. Some friends that mean the world to you see you as a distant addition.
I do have childless friends and single friends and those are more reciprocal. I think that it's hard to have relationships when one of you has kids and the other doesn't as they are such different places to be in, socially and emotionally. Neither side is to blame.
I also think that there has been a massive shift in socialising and sense of community. In my parents generation it was common to see friends and have hobbies etc whilst the kids were small and once they had grown up. Now, not so much, especially since COVID. It's increasingly common for people to focus only on their job, partner and or kids and there isn't anything left over for anyone else. So I think it's harder for single people without kids to find community and a sense of a place in the world etc.
As an aside, I've often seen posts from mums who explain a similar need for friends and community once kids leave home, they say they didn't really have time for this whilst bringing them up and all of a sudden there is a lot of time and space and they want to fill it with others.