The Queens mom who ​sickeningly ​posted photos of her dead 11-month-old son on Facebook after ​smothering the child in a sheet ​told cops every twisted detail about how she took a long shower ​while he helplessly suffocated​, and then dressed him up for the photo, new court papers ​allege.

Nicole Kelly, 22, was arraigned on murder and assault raps Thursday in Queens Criminal Court for the death of ​her son, Kiam Felix, Jr.

“I tucked his entire body underneath the sheet to make sure he couldn’t breathe. I got in the shower and took a longer shower than usual,” Kelly told cops, according to court papers released after her arraignment. “After I got out of the shower I checked on him and he wasn’t breathing. I cleaned out all of his stuff from the apartment and dressed him in his suit.”

The unbalanced mom then posted ​to Facebook ​a photo of Kiam’s corpse dressed in a white suit and tie with the caption “RIP Tinkabutt,” authorities have said.

Kelly described the cold-blooded killing to cops after saying she had “snapped” and, “I was done being his only caretaker,” the court papers state.

“The defendant intentionally suffocated her own child while she callously took a long shower,” ​charged Queens ADA Brian Hughes ​at the court hearing​.

Kelly​, who had been held at Elmhurst Hospital on a psychiatric evaluation ​since her arrest, came to court dressed in a hospital gown and held her head down – speaking only to answer “yes” when the judge asked if she understood the proceedings.

Kelly even told cops she would rather her son died than live with another family.

“She had previously decided that she no longer wanted the baby and did not want the baby to go to foster care,” the court papers say.

Kelly only admitted she meant to kill her son Sunday in their Elmhurst apartment after making three previous statements in which she made it sound like an accident, but in her final statement she said she watched her son struggle under the sheet and she knew he couldn’t breathe, the court papers state.

Defense attorney Scott Bookstein entered a not guilty plea and said he would fight the charges against Kelly, “all the way to the end,” noting that the charges against her were exclusively based on her statements.

She was remanded without bail after Bookstein said he would investigate the death before making a bail application.

Before her arrest Kelly posted a rambling Facebook screed in which she said she failed to “protect” the boy.

“Missing my baby boy so much wish there was some way I could bring him back to life,” Kelly wrote. “I feel horrible knowing he passed away Am his Mother I was supposed to protect him I know his spirit will always​ ​be around me…”

Her posts drew furious reactions on social media after she was arrested.