Aw, Chai Tea, I'm sorry. I've had to do that a number of times, being a life-long lover & owner of cats, & it's never easy. But what a grand old age Lulu reached!
Was she a tabby by any chance? My theory is that they are the longest livers, especially if female. My Polly cat lived to 23 & wasn't sick at all through most of her tabby life. She just got a wee bit wobbly on her legs & vague in her last couple of years. But cranky till the end!
As Vivien said, you can't ever "replace" a beloved critter. Each one is totally different. But they (or their memory) stays with you once they die. You don't ever forget them. For example, a few pages back on the this thread, I was doing a couple of "memory raves" on 2 of my departed cats: Rats & Ms Mozzie. And I can still remember precious cats that were my constant companions when I was 5 or 6 years old. They certainly make a lasting impression, these critters!
So, Chai Tea, even though you're feeling very sad right now, I hope in the not too distant future you adopt another cat. (Who will no doubt turn out to be marvellous & totally unique!
) & that you'll be telling us all about her/him on this thread. Welcome to A2K!