One month ago we rescued a pregnant cat from a risky area. People who knew her there told us she already got pregnant about 3 times before, but they never saw the kitens and they suspected someone killed her previous litters. So we took her in and two weeks later she had the kittens.
She was a little aggressive towards the humans of the house when pregnant but became much calmer and even friendly after the birth, rubbing against us, meowing softly when she saw us, showing her belly. She let us handle the kittens with no problem.
But now she's attacking the other cats in the house, unprovoked and without warning. Yesterday she attacked one of our fosters from behind, without hissing or anything, she just lashed out on him.
I feel like locking her up with her kitties won't do a lot of good in the long run, besides, she hates being locked up and she's always asking for attention and head rubs.
I feel like she's bored out of her mind and has no escape for her energy, but I've tried playing with her with a toy stick (those with feathers in one end), and she absolutely ignored the toy.
How can I help her calm down with the other cats and also let out some steam?
She's about 3 years old, healthy, fluffy, and has 5 kittens.