Her mother, Rocio Perez, was determined to make her daughter happy, using her income tax return and a small loan to make it happen in April 2016.
Karen never got to see the photos from her big day. She was raped and murdered by her boyfriend not long after.
Rocio says the weekend her daughter went missing, she already knew she was not alive.
SEE MORE: South Houston teen who killed girlfriend and put her under the sink shared graphic images of her murder
She was last seen on surveillance video at a restaurant with her boyfriend, Jesus Campos Jr.
Karen was missing for three days when Campos told his father, "She is not alive." Investigators then found Karen's body at an abandoned apartment complex.
"It was something very painful," Rocio told ABC13 in Spanish.
Fast forward to this week, when Campos was found guilty of capital murder and sentenced to life in prison.
"I have no pity for him," Rocio said.
VIDEO: Teen's rape and murder caught on cell phone
She also told Eyewitness News that up until this year, she never truly knew how her daughter died until she was in court, where gruesome details, photos and videos were shared.
She said Campos took a picture of Karen's lifeless body as he stepped on her face.
"That's the photo," Rocio said, "that caused me the most pain."
Karen's mother said Campos will pay for what he did in prison for the rest of his life, and she's glad he won't be able to harm anyone else.
Follow Mayra Moreno on Facebook and Twitter.