Nature's Miracle makes a great cat litter that I love. It's 100% natural, clumps well and does a decent job of covering up the odor, and, it's flushable! I know that a lot of people also love World's Best, and Feline Pine (although FP won't cover the poops).
How big is the litter box? Is it kitten sized or adult sized? If it's an adult sized switch it to a kitten sized, it makes it easier for the kitten to get in and out of.
Also has your kitten been dewormed?
Do you have other cats?
If possible keep the litter box away from her eating area. Most cats don't like to eat near to where they do their business
When washing the litter box itself, just use plain ol dish soap and hot water. Don't use harsh chemicals like bleach as certain smells can repulse the animal. Remember cats go by smell and if their box smells all chemically and weird to them...well, you get the picture. Not to mention the residual fumes can harm them.
Hopes this helps, please keep us posted.