A semi feral cat in my garden keeps having kittens?

[~ Empire Of The Sun ~ <3]

I have tried to catch her but shes too fast and claws you to death if you try to pick her up, but she lets you stroke her and hold her kittens - odd cat. I read that feral cats can have up to 2,000 kittens over 5 years and im fed up of bringing in litter after litter looking after them from 4 weeks and finding them homes, what should i do
ive spent lots of time with her, everyday i stroke her and feed her for almost a year.