Try clay litter instead of crystals. I had a cat who refused to go in the box with crystals. And since she is under 12 weeks, you need to use a non-clumping litter.
Put her in the box, and move her front feet to show her how to 'bury'. She was raised outside and doesn't know how to be a cat yet. She needs to be taught.
Sounds a bit like this vet is not great. Are there other clinics around.? Cats can be neutered at 6 - 14 weeks or 2 lbs (pediatric neuter/spay).
They must not have contact until this is done or you will have a huge problem. Your male cat isn't jealous, he's just responding to his hormones raging. He needs the snip soon as possible.
I know a good vet but it's gonna take some time to convince my parents to neuter him...It was really hard for them to recover after the previous cat's death.
I'm gonna keep her until she learns to use the litter box.
This is new to me, because all the kittens that I found on the street used the litter box immediately...
I'm visiting my friend tomorrow and she has a cat too, and I'm gonna ask her to give me a small bag of litter, cause the one that she uses it's different than mine.
Thank you all so much for your help!!! I will keep you updated.
OH MY GOD THIS IS HUUUUGE!
SHE FINALLY POOPED IN THE BOX.
Actually she pooped in both boxes...I am so proud.
I was starting to feel guilty for not letting her poop for so long but it finally paid off.