Shortly before beautiful New York City graduate student Imette St. Guillen was brutally murdered, her best friend called her to try to coax her into going home and ending her night of partying.

But instead of heeding her friend's advice, Imette went to another bar — and was found dead 17 hours later, nude and violated, wrapped in a cheap flowered quilt, bound hand and foot with a sock shoved in her mouth, her hair lopped off and her face wrapped like a "mummy" in clear plastic packing tape.

In the chilling telephone exchange, Imette told her closest pal, Claire Higgins, that she wasn't ready to call it quits partying, investigative sources said.

Claire had just taken a cab home from the a downtown bar, where she and Imette had spent 4 1/2 hours drinking and socializing.

But when Claire got home, she felt uneasy about leaving her friend and called her, a source said.

Their brief exchange didn't make her feel any easier.

"Where are you?" Claire asked.

"I'm in another bar," Imette replied on her cellphone over loud chatter and music in the background.

"When are you going home?" Claire asked.

"Later. I'll be home later," her pal said.

That was the last anyone heard from the bright Boston native, who had been studying for her master's degree in forensic psychology at John Jay College of Criminal Justice.

Her body was dumped in a patch of weeds along a desolate stretch near a parkway in Brooklyn.

While partially hidden, the corpse could still be seen from the street, leaving sources to speculate that her killer left her there, rather than completely hide her, because he either wanted her to be easily found or he was suddenly interrupted and had to leave quickly.

The young woman — who would have turned 25 Thursday — was wrapped in a white, commercial-grade bedspread bearing a Monet-like design of red, pink and purple flowers surrounded by green leaves, possibly from a cheap motel.

She had been suffocated, strangled and likely raped and sodomized.

Cops said the petite, 5-foot-2 Imette fought desperately for her life, ripping off several of her fingernails and bloodying her fingers as she tried to fend off her attacker.

But the psycho killer overpowered her, shoved the sock in her mouth to quiet her, and bound her hands with wire and her feet with shoelaces.

And either then — or hours later — he covered her face with tape to suffocate her, and used a ligature to strangle her and finish her off, sources said.

If he was a real sicko, one detective said, he probably used the clear tape so he could watch her frantic struggle to breathe.

St. Guillen's grieving widowed mother, Maureen, and lookalike older sister, Alejandra, wept as they appeared on national TV last night to appeal for the killer to come forward.

"I used to call her 'La Reina,' the queen, because of the way she carried herself," Maureen, her face streaked with tears, told a news network. "When she walked into the room, the room lit up. . . . She was such a good person."

Alejandra, who lives in Boston along with her mom, fought back tears as she added, "Anyone who heard anything, saw anything ... this was our baby girl and someone took her and hurt her in a really, really bad way.

"She loved New York, [it] was her home. ... She deserves to have this person or people be brought to justice.

"If this had happened to somebody else, and she had seen anything, she would come forward."

Imette — who graduated magna cum laude from George Washington University in Washington, D.C., — had just returned home from a family vacation in Florida before her death.

She flew back Friday morning, arrived at her uptown apartment shortly before noon and immediately got together with Claire, according to a police source.

The pair — buddies since their high-school days at the elite Boston Latin School — hung out together most of the day and then, at about 10 p.m., decided to go out and party.

They went directly to the Pioneer Bar, where they drank and chatted with other patrons — neither of them talking or spending time with anyone in particular, sources said.

"They were just out having fun," one source noted.

But at 2:30 a.m., Claire, a city high-school English teacher, wanted to go home.

The two left the bar — and, as a surveillance videotape revealed — they began debating outside about whether to split up

Claire wound up hopping into a cab and returned to her apartment, never again to see her friend alive.

A source close to the investigation said the likeliest scenario of what happened next to Imette is that she met someone at the second bar she went to and left willingly with him.

But then, the source said, something went terribly wrong, and Imette rebelled — perhaps at sexual demands being made of her or perhaps at the appearance of other men on the scene.

Other investigators theorize that Imette decided to go home and got into a taxi, somewhat drunk, and was attacked by the cabby.

Still others fear she fell prey to a psychopathic sex maniac, although an initial search of FBI files for similar crimes in the area came up empty.

When Imette failed to return to her apartment by late Saturday morning, her friends and relatives began searching for her.

At 8:20 p.m., a phone tip about a body led police to a notorious gangland dumping ground off the Brooklyn beltway.

Police believe St. Guillen's body had been dumped there a short time before they got the phone tip — which came from a payphone outside a diner a mile and a half away.

They also believe the call may have been made by the killer or someone linked to the murder — either out of remorse or for attention.

Investigators have been checking hotels and laundries that do dry cleaning for hotels in an effort to find out where the quilt came from — and where Imette may have spent her last hours.

The quilt, packing tape, wire and shoelaces are being examined for prints and DNA, and tests are being run to see if there's any evidence of the killer's skin under Imette's torn fingernails.

Sources said no semen was found.

In addition to Claire, detectives have interviewed a number of Imette's friends.

Among them were two of her male acquaintances — one a former boyfriend from Boston, the other a fellow student at John Jay.

Both were ruled out as suspects, officials said.

St. Guillen's sister and mom insisted that if there had been someone stalking her or been obsessed with her in the past, they would have known.

"We were very close ... and if anything like that was happening, she would have told us," Alejandra told Cosby.

Her mother said she believes that the case will be solved.

"She lived so much. She would have been 25 this Thursday," Maureen St. Guillen said.

Then, breaking down again, she added, "And it just wasn't enough time."