No, it's not about appearance at all. Like SGB, I have a real issue when other women seem to instantly take a dislike to a beautiful woman and want to put her down and find other "faults" in her.
The behaviour I think many of us dislike is when a woman appears to be doing a mental check on meeting you; looking you up and down, assessing what dress size you are, your clothes, your face, your hair - and comparing instantly whether in her opinion, you are more/less attractive than her. It's so obvious when it happens - people's body language and facial expressions betray far more than they realise.
This is often accompanied by the other behaviour described: valuing men's contributions more, literally "seeing through" the women in a group and dismissing them, when in discourse about another woman, focusing on that woman's appearance first, before any of her other attributes are discussed, denying that sexism exists, being more forgiving of male faults and excoriating about women's (men will be men etc.).
As an observation incidentally, these are just the sort of women who vilify ex-wives, blame women exclusively for why their marriages ended, run themselves into the ground trying to be the perfect woman for "their man", pretend to like porn and accuse women who dislike it of being insecure/sex-haters and the theme that runs through their lives is that they see all women as competition and rivals in a marketplace.