Litter box problems

I am new to the forum and I have been having problems with one of my cats. I saw several posts regarding litter box problems but none of them matched the problem I have.
About 3 months ago I adopted two cats. One old male, they weren't sure on the age, and a one and a half year old female. The problems I am having are with the female. When she uses the box she never covers up her waste, pee or poo. This wouldn't be so bad but it doesn't allow the litter to do its job at fighting odors and my laundry room is really starting to stink. What can I do to encourage her to cover it up?
The other problem is she occasionaly sits in the box to poo but hangs her rear over the side and poops on the floor or the side of the box. At first I thought it might be due to the box being to dirty but I have been cleaning both of the litter boxes out religiously at least once a day and it still happens once in awhile. Any ideas?
Thanks in advance for any help

Hello & welcome to the forum. A couple of questions - is the litter box big enough for her? & what are you cleaning the box with? Cats don't like strong smells. I clean Blossom's litter box once a week with hot water & a scrubbing brush, drying in the sun. I
take out the solid waste out when needed.
To get her to cover, perhaps gently take her front paw & scratch in the litter after she's been. This is what I did with Blossom as I've had her since 3 weeks & had to show her how to use the litter box & scratching post.