"Pay your outstanding balance, or release your apartment and turn in your keys to the leasing office by 60pm today," it read.
"Eviction will be filed promptly Tuesday morning, 8/18/2020."
The mother posted the letter online, writing, "So y'all think it's funny to antagonise the person that's going through financial hardship with putting an emoji stating, 'Guess who's moving today?' There was nothing funny about that."
But Ms Lee had the last laugh. She has now landed a new job and home.
When she found the note, "I was mad, I ain't going to lie," Lee told People magazine.
"I felt like they were antagonising the tenants through the situation and it was heartless, especially during a pandemic.
"A lot of people have lost their jobs. A lot of people aren't able to get the resources.
"I'm a single mother with two boys. I do the best that I can and am a very hardworking woman," she added.
Ms Lee lost her job at a local food chain at the start of the Covid-19 pandemic in March.
However, she was unable to receive unemployment benefits.
After failing to pay rent in June and July, she told her property manager about her situation, expecting sympathy.
Karya Property Management, who owns the complex, has since apologised for the notice and said the manager who left it has been disciplined.
"I am apologising personally in case it was insensitive, and if she was really trying to work out a payment program with the property or that she was in communication with the manager, then I accept it's truly our fault," said Swapnil Agarwal, the CEO, in a statement.
Ms Lee's plight soon made national news, with the American Broadcasting Corporation picking up her story.
More than US$34,000 was raised to support her and her family.
"It's been so overwhelming, and I am so grateful. I have never experienced anything like this," Lee said.
She has been able to afford two months of rent, had her electricity bills paid for by strangers, and received new school supplies for her two sons.
Lee also landed a new job that she begins today.
"I have to pay this forward 10 times fold," she said.