Mummy cat attacking her kitten

Question
Hey,

I'm not a hundred percent this is in your area of expertise, but there weren't any experts in the cat behaviour bit so...

My cat gave birth to four healthy kittens about four/five weeks ago, she's been plenty fine with feeding and grooming, but recently she's started attacking one of the kittens. The cat (Idgie) was originally a half stray, the only contact she had with people was feed time, or when her owners kid chased her across the yard.
The kitten she's been attacking is the only boy of the four, largest of the lot, and is a little aggressive himself, but only as much as she's taught him to be. Idgie has never had much of a personality, she's never shown signs of aggression unless you count the scratches I get when holding her while she's freaked out of her mind (or hissing and snarling at puppies). She treats the other kittens fine, and this isn't her first litter, her first had only one kitten though, who we had to get euthanized due to this rare disease that stopped it being ale to walk and caused it a lot of pain. Idgie got a chance to say goodbye to her baby before we buried her.

The kittens she has now, they have never really been confined to one space, the moment they started crawling out of the first little 'den' Idgie had, we convinced her to move them to a bigger box, and encouraged her to let us bring said box into the lounge, because my room was too cold for the kittens, especially when Idgie decided she'd had enough of feeding them and went walk-about. She was fine with it after a while, at first she'd try picking them up and dropping them, roughly, under my bed. Where they likely would have gotten too cold, and sick.

Idgie is a skittish cat, at the first sign of danger (aka loud noise, new people, old people she never liked, vacuum cleaner etc.) she will run and take cover under my bed. (Or claw my arms out, because half the time I'm holding her, trying to de-scare of things she has no reason to be scared of)

The kitten she's been attacking is the only boy of the lot, she has been known to hiss at the neighbours cats through the screen door (both male) but when outside with them she's more than friendly. Idgie has never been properly accommodating of Pepsi (the kitten) she always, ba when he was born, kind of let the other kittens feed first. (He was born first so she couldn't exactly dictate when he fed then)

Yeah. I can't think of anything else.

Please and thankyou ^-^

(oh and how to get kittens used to collars?)

Answer
This is not easy to answer.
but first I would certainly get Idgie desexed.  Raising skittish kittens is not a good idea.   A Pregnant cat that you cannot treat should she need care is not a good idea...so desexing Idgie would be first on my list of to do things.

In the wild mom's naturally move their kittens....and they can safely leave them and do a walk about after about 5 days.....in the wild mom would have to go and hunt anyhow.
A nice warm bed under your bed  might make her happy.

Holding a scared cat is not a good idea.....you cannot make her unscared that way. You just get scratched and she becomes more scared.

As for attacking the kitten I am not sure...is she really attacking him..hurting him??? or just roughly trying to keep him in line so to speak....
Kittens should not wear collars before 12 weeks of age and then only the safety kind that break away.....I have never had an issue  I just put them on them and let them go about their business...if they are too young it is dangerous.