Tiger Is Dying. When?, Elderly kitty dying Options

[Tiger's Mom]

My 18 year old kitty is dying of kidney failure. Her lab values are through the roof, she's less than 5 pounds now, she wobbles when she walks, and now she barely eats. I've been giving her SQ fliuds each day for about a week. She can't seem to get her tongue to sit right in her mouth and fiddles with it. All of this has transpired within the last 2 weeks.
This is heartbreaking. I've had cats and dogs all my life, but you know how every once in awhile a special one comes along? Well, Tiger is special. She follows me everywhere, and talks alot. She's only content to sleep at night if her paws are resting on my hand. She gets in my face, tickles me with her whiskers, and meows till I hold my hand out for her to put hers on. She plays with a little toy on my bed just like she was a little kitty. She would race around my bed in circles and pounce on imaginary mice to make me laugh. I have 3 younger cats that like to play too, but the speed of Tiger's paws is twice that of the other cats. She was so fast my daughter and I jokingly call her Miss Miagi (like from karate kid).
Now, I'm tortured with when/how to decide to have her put to sleep. Until today she seemed comfortable. Today, she's acted restless in spite of her decline, wandering the house, so I think she's uncomfortable. My sister, who grew up with Tiger as well, describes her as not a regular cat, more like a funny little fairy or angel. Letting go is just horrible.

[Tiger's Mom]

I do not have the what if's, or any regret for I know it was the time and didn't want her to suffer more than she already had. But, am left with an empty hole where she used to be. She was my constant companion, very vocal and expressive. Like a little angel that would always try to talk to us. When I did my work at the computer, she'd always meow till I set her on my lap. She'd prefer to stay in my bedroom, but would always run down when I came home, and meow till I followed her upstairs. She'd run in circles on the bed to make us laugh, and pounce on invisible mice. She slept with her paws on my hand at all times, and would wake me with her wiskers, and her big eyes an inch from my face. We miss her so much. I try to focus on all those special memories.

Thank you all so much for the support. It's is very comforting to know others understand.

Elizabeth