She was at the hospital in serious condition, officials said.
Police said they received a call about a stabbing around 7:30 p.m. Tuesday near the intersection of West Alpine Street and Palm Avenue.
When they arrived, they found the woman on the ground and the home engulfed in flames.
"We were panicked, we were worried and then the fire just got bigger and bigger," said neighbor Sabrina Vargas. "The entire community came out. It was just pandemonium."
"I heard a lot of noise, a lot of yelling," said Frank Williams, who lives across the street. "Three kids were running down the street talking about their grandmother. Their grandmother was dead."
There were at least two people with blood on their clothing seen running away from the home, said Upland police Lt. Cliff Matthews.
Descriptions were not immediately available.
Some neighbors said there was frequent police activity at the home.
Anyone with information is asked to contact Upland police at (909) 946-7624.