Very rude thing to say or imply.
Although it does seem that many people - women especially - seem to want a daughter. Not exactly sure why. Different reasons for different women I guess. I know loads of people who don't dislike boys, and are happy with having sons, as long as they have at least one daughter.
There's just something about having a daughter that you simply don't get with boys. It's hard to put into words. Some people I know who have boys only, say they feel the people they know with daughters, are closer to them than they are to their sons. Also, the children that their sons have with their wives, are closer to the maternal grandparents.
And there is sometimes a clash between women of sons, and their daughter-in-laws, and the sons always stick up for the wives. I know several women with sons who have virtually non existent relationships with their son(s) because of conflict with the DIL, and also, they never see the grandkids.
I don't know a single woman with daughters who have this same thing going on. I am not saying it never happens, just that I have rarely seen it - if ever.
Oddly, many years ago, (pre 1980's) many mothers seemed to be desperate for a boy, and boys were revered and preferred. I think many a woman over 45/50 can tell a tale of how their mother preferred their brother(s) and their aunts preferred their male cousins to their female ones...
But things seem to have shifted this past quarter century or so, and women seem to largely want at least one girl (in the western world anyway.) Maybe the mother preferring their brother when they were kids is another reason they desire a daughter - to try and create the mother-daughter relationship she never had with her mother.
I do still think what the woman in the OP said is very rude, but she is right; many women do seem to want a girl. I think some men want a daughter too, but don't mind a son so much ... I know many men with all girls, who are as happy as a pig in muck with their daughters.
Finally, I find mothers with one son only - when he is the only child - are perfectly content and happy with their one boy. They are also positive about girls/other peoples daughters... However, some women with 2 or more boys seem quite snide and bitchy about girls, and are very vocal about how they would never want one.
It's either because they wanted a girl, and it's a defence mechanism, or they are sick of people titling their head and pitying them for having all boys, when people with all girls get told how lucky they are...
Not ALL women with 'boys only' are like this, but I have encountered quite a few. Yet I have never experienced mothers with all girls behaving like this.
Without a shadow of a doubt though, many people want a daughter. More so than a son. If they could have only one child, I genuinely believe the vast majority of people - especially women would pick a daughter.
JMHO.