Paper will not help contribute to her being the suspect. A blade is more efficient. However, there are some YouTube vids out there which depict fashioning a blade out of paper--notice though that other materials are used (such as tape, and in one case a screw) or have a metal base.
It would be laughably easy for a forensic pathologist to tell that the wounds are self-inflicted.
This method is not realistic because
a) It's more likely to result in a failed attempt.
b) He would not be done before she gets out of the shower. Look at the depth of a paper cut. Then look at how deep you'd have to go and through what you'd have to cut. Even the external carotid is protected by more than just skin.
c) The "sheets of bloody paper" you're picturing all around the body would not be able to be fashioned into a weapon good enough to get the job done.
d) Because the method takes so long and there are a lot of cuts to be made, any forensic pathologist would have ample evidence that the cuts are self inflicted. For her to have done it, he would have had to have been unconscious. Deeply unconscious. Otherwise he'd have defensive wounds and he would not have stood still for it. If he stands or lays or sits or shifts, the blood drops will tell their story and exonerate her, even if it is possible. Even if he takes a drug to mimic that he was unconscious, they can test for how much of it actually got into his system--how much of it is actually incorporated into the blood spilled, and still in his body AND internal organs. Also his hands will end up bloody. If he cleans them evidence will be in the room. If he wears gloves, the gloves will be in the room, and will have his DNA inside.