“Females don’t get along” – any science behind this?

I ask because in the country where I live, EVERYONE says this. Like when another dog owner sees my dog on a leash, they ask “girl or boy?” And when I tell them girl, they say “oh ok, mine too, better not let them get too close”.

Where I grew up (different country) I honestly never heard this. We have lived in both countries with the same female dog (now age 10).

Now we’re adopting another female dog (puppy, 3ish months old, will be spayed ASAP) and the adoption agency is suggesting a male might be better and more compatible. My dog (spayed female) cannot stand male dogs, especially male puppies 😂. All of her besties have always been females.

Any insight into this? Checked on Google Scholar but I don’t really see anything… even though the internet is full of blogs that confirm it’s true.