Sudden change of behaviour

[reallyisthisallthereis]

I have a female cat age 7 and her two sons. They've always got along fine but 2 days ago the female has started attacking both boys. I watched her earlier come up to one of her sons sleeping on the sofa and give him a good sniff, then go for him. He's bolted out of the house. We've heard this happen about 4 times yesterday including in the middle of the night. She's really been aggressive at that and treating them like strange cats in the house.
Any ideas what might be causing the sudden change in behaviour. We have covid and I'm wondering if she may have caught it and lost her sense of smell?

Any sudden change in behaviour with no simple explanation requires a vet check.

She could be in pain, or she could be having issues with her sight/hearing.

How old are the sons? Kitten age or adults? Are they all neutered? Any behavioural issues before now?

Sons are 6 years old

I’d take her to the vet too, have you seen any strange cats in the area? Sometimes that’s enough to upset the equilibrium in multicat households.

Both neutered. Out of the 3 of them, she's always been the territorial one who chases off other cats/ dogs and even the fox, despite being tiny herself.

Her behaviour with us is normal so it's just her two sons that she's attacking so I don't think it's not eyesight or hearing or she would be nervous with us too.

I'd also get a vet check. But my usually placid cats went crazy with each other when another can't came into their garden.

We've both got covid so may have to wait a few days before we take her but I'm going to ring them and see what they say.