Notre Dame grid star Manti Te’o quickly replaced his fake dead girlfriend with the real thing — a stunning Indiana college student, according to friends and the couple’s Twitter feeds.

Weeks after his bogus online girlfriend, “Lennay Kekua,” supposedly died of leukemia, the linebacker was keeping company with Alexandra Del Pilar, the 21-year old daughter of an Indiana cancer-center doctor.

Del Pilar — from Notre Dame sister school St. Mary’s College — first provided a real shoulder for Te’o to cry on when his grandmother was dying last fall, a source told The Post yesterday.

“When he was going through all the trouble with his grandma in September, that’s when he started talking with Alex,” the source said.

Kekua also was supposed to have died in September.

By October, Te’o and Del Pilar were spending more and more time together.

“Just making sure Manti gets home for the game tomorrow!” Del Pilar tweeted on Oct. 26, along with a photo of the linebacker clad in his uniform and sitting in the passenger seat of her car.

On Nov. 15, Te’o tweeted, “Always and forever,” and Del Pilar retweeted it.

The next day, Del Pilar posted a picture of a colorful floral lei hanging from her rearview mirror, with the tweet: “Thank you @MTeo_5 for making my car smell so good :)”

By January, Del Pilar was being teased about the relationship by Notre Dame players Lorenzo Wood and TJ Jones, with Jones tweeting that Del Pilar was ignoring them and Wood writing, “she is to good for us now that she is with u know who!”

One of Del Pilar’s closest St. Mary’s friends is from Hawaii and went to high school with Te’o. On Jan. 7, the two women, clad in Fightin’ Irish gear, mugged for the camera in Miami at the Notre Dame’s national championship game.

Te’o has said he only learned Dec. 6 that his previous online-only “girlfriend,” Kekua, never existed and was an elaborate hoax.

That day, Te’o got a call from the woman he had thought was Lennay, saying she wasn’t dead, a source close to Te’o told The Post.

She said she had to fake her death to get away from drug dealers who were trying to kidnap her, the source said.

“He was shocked, and he didn’t believe her. That’s when he told the school and his family,” the Te’o pal said.

Two days later, Del Pilar posted a curious tweet: “ ‘A lie can travel halfway around the world, while the truth is still putting on its shoes’ – Mark Twain.”

That same day, Te’o was beaten out for the Heisman Trophy by Texas A&M’s Johnny Manziel, with Del Pilar tweeting an encouraging: “Still # 1.”

Te’o finally ended his silence last night in an interview with ESPN.

“I wasn’t faking it. I wasn’t part of this,” he said.

“When (people) hear the facts, they’ll know. They’ll know that there is no way that I could be part of this.”

Te’o, according to reporter Jeremy Schaap, said he lied to his father about meeting “Kekua,” which later led to the dad telling reporters the fake couple had in fact met.

Schaap also said Te’o “suggested to people” he met “Kekua” before she “passed away” because it would “be too embarassing” to admit they never met in person.

Meanwhile, a longtime Te’o friend yesterday said friends of the gridiron star first “met” Lennay Kekua on the phone during a 2008 party in Provo, Utah.

She introduced herself as a cousin of Ronaiah Tuiasosopo — the man now fingered as the mastermind of the scam.

“Lennay,” according to the source, eventually reached Manti on her own by phone.

Te’o has said that he knew her for four years and that the pair started “dating” in October 2011. But at one point that fall, Te’o was asking pals whether “Lennay was real,” the source said.

Del Pilar and Tuiasosopo declined comment.