It’s because of differences in gender socialisation. You know how there’s a toxic masculinity? There’s a toxic feminity as well.
One aspect of it is you must support “your fellow sisters” regardless of what they do otherwise you hate all women. Or that you must support your (female) friends when they do something bad otherwise you’re not their friends.
Toxic masculinity is more individualistic and toxic feminity is more collectivistic. Both in excess are bad.