Angry cat and other cat's kittens?

by Emily
(Texas)

We have 2 cats who got along fine, even licked each other. Well, one gave birth to three kittens, and our other cat wasn't fond of them at all.

She'd growl and hiss if they came near. But we expected that and just waited for them to get along eventually. And eventually, it happened.

Our other cat warmed up and loved the kittens, licked them, slept with them, even got worried if they wandered off too far. We thought it was adorable.

But suddenly out of nowhere, she began disliking the kittens again, back to hissing, back to growling. She even picks fights with our other cat. What happened? Why does she suddenly not like the other cats after loving them for so long?