UPPER EAST SIDE — An Upper East Side real estate broker and cancer survivor was harassed by her landlord and evicted from her apartment because her management company was afraid she wouldn't be able to pay the rent if the illness came back, she claims in a federal lawsuit.

Heatheran Kristopher, 43, said she was forced out of her $2,250 per month apartment on East 81st Street by a landlord who began hounding her within a month of taking over the building in 2011, according to the lawsuit filed Jan. 25 in Manhattan Federal Court.

"I feel completely alone, I feel completely lost right now," Kristopher told DNAinfo.com New York Monday, as she stood inside her empty first-floor apartment at 336 E. 81st St.

"I know it's only an apartment, but it's just what I went through here. I healed myself here. I came home from chemo and laid in this backyard. I feel safe here."

"There's nowhere else I can turn at this point," she added, saying she's crashing on friends' couches while she tries to find a place to live.

Kristopher said the high-pressure bid to force her out of the building began in September 2011, less than a month after Stone Street Properties LLC bought her building from the previous landlord Icon Management.

She said she had signed a new two-year lease with Icon in August 2011, but had not received a printed version of the lease by the time Stone Street Properties took over.

According to the court papers, Stone Street co-founder Robert Morgenstern showed up at her door unannounced in September 2011, and began shouting at her that she owed him $5,000.

When she told him she had cancer, he allegedly snapped.

"How do I know you're not going to get cancer again?" Morgenstern yelled, according to the court documents.

Kristopher, who recently founded her own real estate firm, had lived in the apartment since 2008, just before she was diagnosed with ovarian and colon cancer and began chemotherapy and radiation treatment at Memorial Sloan Kettering Cancer Center, according to the lawsuit.

She had fallen behind in rent by more than $10,000 during her cancer treatments, but had caught up by the time Stone Street took over. She wanted to stay in the building in part because of its proximity to Sloan Kettering and because the first floor home made it easy for her to move around.

"They were doing anything and everything to get rid of me," she said.

Stone Street staffers began to insist that her new lease was invalid and refusing to honor its terms, the documents said. Instead, they urged her to sign a six-month lease.

"This way you're not locked in if you do get sick again," Stone Street leasing agent Cody Moore allegedly said. "I strongly suggest you sign this or you will be put on the black list."

Stone Street also tried to increase the rent by $700 per month and get her to pay six months rent up front, the lawsuit says.

On Nov. 22, 2011, the landlord filed a petition to evict Kristopher and a week later she filed a disability discrimination claim with the New York Division of Housing and Urban Development and the New York State Division of Human Rights.

After a nearly seven-month investigation, the New York State Division of Human Rights found that there was "probable cause for discrimination on the basis of [Kristopher's] disability," according to a report dated May 25, 2012.

However, the agency did not find evidence that Morgenstern moved to evict her because she filed the complaint with HUD. Kristopher later withdrew the human rights complaint in order to file the federal lawsuit.

Kristopher won a number of delays in the eviction proceedings, but she was forced to clear out Monday after the state Supreme Court upheld the removal.

"She's a sour-grapes tenant who was evicted because she had no lease," said Morgenstern, who denied making the cancer comment.

"I categorically deny any wrongdoing."

Kristopher, a spokeswoman for Ihadcancer.com, said she went to war with the building to protect herself — and to help others who might find themselves in the same boat.

"I'm an advocate for cancer patients. I work with cancer patients. I volunteer, I go to chemo with them," she said. "I'm not going to allow this to happen."

As part of the investigation, HUD asked Stone Street for a list of other tenants in the building who had fallen behind on their lease and were also then offered a six-month agreement, according to the investigation report. The company failed to provide the information.

While she does not hold any illusions about getting her apartment back, Kristopher said she hopes the suit will dissuade other building owners from discriminating against people in similar situations.

And she is committed to staying in the city, in part to honor her mother, who lived in Manhattan until she died of cancer when Kristopher was 10 years old.

"I feel close to my mom here. Every day everything reminds me of her," she said.

"I'm just going to fight this until the end. I have to. It makes me feel not like the victim."