Why does Katie always seem so adamant about having fillies?

!Not snark! so please don't use this as a way to be hateful nor take it as me being so.

I believe I saw her talk about it before as to why she want's them, I just forgot.

Don't get me wrong, I don't think there is anything wrong with a preference and she clearly does not dislike/hate the colts, but sometimes It can be very clear to see the disappointment when the foal is a male.

But to me, the only reason I could think of Is since she is a breeder, to have more potential mares to breed later on in their lives. However with that being said, she has so many mares and way fewer male horses, including only 3 stallions, 2 actually able to breed, so wouldn't having more colt's mean more stud prospect potential? Or is there another reason she prefers fillies?