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This is a pretty unhappy cat. Behavior such as this is almost always a "protest" action, given that she is otherwise healthy.
What's her normal personality like? Friendly? Playful? Sociable? Does she get lots of attention, or does she get ignored a lot?
How long has this been going on? What major changes in her life occurred around the time this began? In fact, has she been doing this all along, or is it something that started suddenly? Or gradually? Did you move in?
Is she left alone in the house for long periods of time? Regularly? Is there a set schedule in her life, or is it chaos?
Did her diet suddenly change? Is she a finicky eater ... that is often caused by low quality, cheap food, and having to eat the same thing all day, day after day for weeks and years. A varied diet provides change and stimulation. Some people put out a bowl of dried food and fill it up once every two or three days. That's animal abuse. Dried food should be kept sealed so it doesn't go stale, and a small portion put out once or twice per day that is about exactly what she will eat.
It's clear she is an inside-exclusively cat. Was she previously allowed to go outside and is now restricted to inside?
Do you keep her litterboxes clean? I care for a cat at my parents house who occasionally used a place other than her litterbox. My parents would clean them once every two days or so; when I'm at the house they get cleaned twice a day. Also, I switched over to clumping litter so that urine gets almost 100% removed from the box instead of leaving a lot behind and festering into ammonia. She only uses her litterboxes now, and sometimes she'll "hold it" and let me know her box needs cleaning before she uses it.
Apart from her boxes getting cleaned thoroughly twice a day, she also gets a lot of direct attention from me. Plenty of petting, brushing, talking with (yes "with" not "to"), and even though she's almost 15, I find ways to get her to play and keep her active.
She grew up with her brother, lived inside a house with him all her life. But he died about a year and a half ago, so she is completely alone now. For a year she walked around the house crying and looking for him. So she is a very needy cat and always wants to be nearby someone. She will wake up crying sometimes and just needs someone to speak with her and touch her, then she settles down.
Is she spayed? If not, she's probably going into heat constantly, which is cruel and unusual torture.
What is her age? What sort of up-bringing did she have?
Cats should never be raised alone. They should always have at least one companion. I always try to have three at a time. They are very social animals; if they are alone with only one or two humans, they literally begin to go crazy, to mentally break down.
Cats require stimulation for their normal cat instincts. If she is not getting this, she is suffering from boredom and depression.
Above all, no matter how frustrating this is, try to never get angry with her, such as shouting, yelling, physical roughness. It will only make the problem worse. I don't mean that she'll pee more, I mean it will become almost impossible to break her of the habit. Right now, if it's a fairly recent development, there's still a good chance to train her.
