The Pinellas County Sheriff’s Office said in a statement that they were called to the Silver Lake mobile home park at 10.30am on Tuesday, where they found the critically injured woman.
The victim, who has been identified as Lisa Rogers Eaton, 56, was rushed to a local hospital with the hatchet still protruding from her head, the sheriff’s office said.
She remained in a life-threatening condition in hospital on Saturday, officials said.
Detectives said that suspect Michael Dougherty, 40, allegedly fled the house where he had been staying with the victim and her husband.
They located his vehicle in Gainesville, 156 miles (250km) north of St Petersburg, and he was pulled over by Alachua County Sheriff deputies in the early hours of Thursday morning.
Mr Dougherty has been booked into Alachua County jail on one count of second-degree attempted murder. He is awaiting extradition to Pinellas County.
Ms Eaton’s sister, Donna Voye, told WFLA that she was not expected to survive and family members had gathered at her hospital bedside to say their final goodbyes.
Ms Voye said her sister and her husband had allowed the suspect to stay with them after he lost his job.
“We can’t understand it because she wouldn’t hurt anybody,” Ms Voye told WFLA.
“No family should ever get a call like we got telling us that their family member is brutally attacked, as our little sister was,” she said.